Guilherme de Ockham

William of Ockham (c.1287–1347)

William of Ockham is a major figure in late medieval thought. Many of his ideas were actively – sometimes passionately – discussed in universities all across Europe from the 1320s up to the sixteenth century and even later. Against the background of the extraordinarily creative English intellectual milieu of the early fourteenth century, in which new varieties of logical, mathematical and physical speculation were being explored, Ockham stands out as the main initiator of late scholastic nominalism, a current of thought further exemplified – with important variants – by a host of authors after him, from Adam Wodeham, John Buridan and Albert of Saxony to the school of John Mair far into the sixteenth century.

As a Franciscan friar, Ockham taught theology and Aristotelian logic and physics from approximately 1317 to 1324, probably in Oxford and London. He managed to develop in this short period an original and impressive theological and philosophical system. However, his academic career was interrupted by a summons to the Papal Court at Avignon for theological scrutiny of his teachings. Once there, he became involved in the raging quarrel between Pope John XXII and the Minister General of the Franciscan Order, Michael of Cesena, over the poverty of the church. Ockham was eventually excommunicated in 1328. Having fled to Munich, where he put himself under the protection of the Emperor Ludwig of Bavaria, he fiercely continued the antipapal struggle, devoting the rest of his life to the writing of polemical and politically-oriented treatises.

Because he never was officially awarded the title of Doctor in Theology, Ockham has been traditionally known as the venerabilis inceptor, the ‘venerable beginner’, a nickname which at the same time draws attention to the seminal character of his thought. As a tribute to the rigour and strength of his arguments, he has also been called the ‘Invincible Doctor’.

The core of his thought lies in his qualified approach to the old problem of universals, inherited by the Christian world from the Greeks through Porphyry and Boethius. Ockham’s stand is that only individuals exist, generality being but a matter of signification. This is what we call his nominalism. In the mature version of his theory, species and genera are identified with certain mental qualities called concepts or intentions of the mind. Ontologically, these are individuals too, like everything else: each individual mind has its own individual concepts. Their peculiarity, for Ockham, lies in their representative function: a general concept naturally signifies many different individuals. The concept ‘horse’, for instance, naturally signifies all singular horses and the concept ‘white’ all singular white things. They are not arbitrary or illusory for all that: specific and generic concepts, Ockham thought, are the results of purely natural processes safely grounded in the intuitive acquaintance of individual minds with real singular objects; and these concepts do cut the world at its joints. The upshot of Ockham’s doctrine of universals is that it purports to validate science as objective knowledge of necessary connections, without postulating mysterious universal entities ‘out there’.

Thought, in this approach, is treated as a mental language. Not only is it composed of signs, but these mental signs, natural as they are, are also said to combine with each other into propositions, true or false, just as extra-mental linguistic signs do; and in so doing, to follow rules of construction very similar to those of spoken languages. Ockham thus endowed mental discourse with grammatical categories. However, his main innovation in this respect is that he also adapted and transposed to the fine-grained analysis of mental language a relatively new theoretical apparatus that had been emerging in Europe since the twelfth century: the theory of the ‘properties of terms’ – the most important part of the logica modernorum, the ‘logic of the moderns’ – which was originally intended for the semantical analysis of spoken languages. Ockham, in effect (along with some of his contemporaries, such as Walter Burley) promoted this new brand of semantical analysis to the rank of philosophical method par excellence. In a wide variety of philosophical and theological discussions, he made sustained use of the technical notions of ‘signification’, ‘connotation’ and, above all, ‘supposition’ (or reference) and all their cognates. His distinctive contribution to physics, for example, consists mainly in semantical analyses of problematic terms such as ‘void’, ‘space’ or ‘time’, in order to show how, in the end, they refer to nothing but singular substances and qualities.

Ockham’s rejection of universals also had a theological aspect: universals, if they existed, would unduly limit God’s omnipotence. On the other hand, he was convinced that pure philosophical reasoning suffices anyway for decisively refuting realism regarding universals, since all its variants turn out to be ultimately self-contradictory, as he endeavoured to show by detailed criticism.

On the whole, Ockham traced a sharper dividing line than most Christian scholastics before him between theological speculation based on revealed premises and natural sciences in the Aristotelian sense, which are based on empirical evidence and self-evident principles. He wanted to maintain this clear-cut distinction in principle through all theoretical and practical knowledge, including ethics and political reasoning. In this last field, in particular, to which Ockham devoted thousands of pages in the last decades of his life, he strenuously defended the independence of secular power from ecclesiastical power, stressing whenever he could the autonomy of right reason in human affairs.

1 Life

William of Ockham was born around 1287, probably in the village of Ockham in Surrey, near London. Of his youth we know next to nothing, only that he joined the Franciscan Order (perhaps as a child), that he was ordained subdeacon in London on 27 February 1306 (an appointment for which he would normally have had to be at least eighteen), and that he was licensed to hear confessions on 19 June 1318 (for which he would have had to be at least 30). He must have studied Aristotelian philosophy – and especially logic – quite thoroughly before turning to theology in Oxford around 1310. Following the normal curriculum, he would then have spent the next seven years as a theology student and have lectured for two years (probably from 1317 to 1319) on Peter Lombard’s Sentences (see Lombard, P.) The commentary that resulted is Ockham’s first major work. It is a huge treatise in four books, the first of which was later revised by the author for publication and is known, for that reason, as the Ordinatio, while the other three, jointly known as the Reportatio, circulated merely in the form of a detailed, authorized set of students’ notes.

This early, and strikingly original, work might already have raised misgivings in certain quarters at Oxford. Whether for that reason or some other, Ockham was not immediately granted the degree of master of theology, which would have entitled him to continue teaching in the field. He was sent instead to a Franciscan convent, possibly in London, to teach logic and physics, which he did from 1320 to 1324. This turned out to be a very productive period, during which he wrote his commentaries on Porphyry’s Isagoge, Aristotle’s Categories, On Interpretation and Sophistical Refutations, and at least part of his commentary on Aristotle’s Physics. He also revised his Ordinatio, engaged in public disputations on various matters theological and philosophical, and wrote a few more treatises on especially delicate questions such as transsubstantiation and God’s foreknowledge. In the same years he may also have begun (or even completed, according to some) his great Summa logicae (Summa of Logic); originally intended for beginners, it eventually became one of the major reference books for the new nominalistic semantics and logic which was to be so influential in the fourteenth and fifteenth centuries.

In the summer of 1324, Ockham left England for Avignon. Most scholars think he was summoned to the papal court there by Pope John XXII for investigation of his teachings. In the previous year a Provincial Franciscan Chapter held in Cambridge had already publicly raised questions about some of his philosophical theses that could be deemed theologically dangerous. In 1325, the Pope established an advisory commission of six renowned theologians to examine fifty-one articles extracted from Ockham’s commentary on the Sentences. The group included the French Dominican Durandus of St Pourçain, otherwise known for his nominalistic sympathies, and John Lutterell, the ex-Chancellor of Oxford and one of Ockham’s fiercest opponents. In 1326 the commission gave a preliminary report, which, while identifying many of Ockham’s opinions as erroneous, did not condemn any as clearly heretical. Apparently this did not satisfy the Pope, and a second report was prepared, much more along Lutterell’s lines. Ockham became officially suspected of heresy, especially with regard to his theory of moral merits, which was accused of Pelagianism (see Pelagianism), and in 1327 Pope John XXII launched a formal inquisitorial process against him.

This process was never brought to a conclusion. However, Ockham in the meantime had got involved in other sorts of troubles. It is probable that during his first years at the Franciscan convent in Avignon, he continued to work on some of his philosophical or theological treatises, such as the Summa logicae, the Quodlibeta septem (Seven Quodlibetal Questions) and the Expositio in libros Physicorum Aristotelis (Commentary on Aristotle’s Physics). Towards the end of 1327 the Franciscan Minister General, Michael of Cesena, who had himself been recently summoned to Avignon by the Pope, ordered Ockham to study John XXII’s bulls of 1322–4 on whether Christ and the Apostles had owned anything and on the poverty of the Franciscan Order in particular. The question was delicate. The papal court was by then scandalously opulent, and John XXII was very much aware of the challenge to it by the advocacy of poverty that had been spreading in many Franciscan quarters in the previous decades. His series of bulls on the subject had been intended to put a stop to this movement. Comparing these with the Gospels and the writings of previous popes, Ockham boldly concluded that John XXII was himself heretical. Matters eventually got worse between Michael of Cesena and the Pope, and on the evening of 26 May 1328 five Franciscans, including Michael and William, fled from Avignon, fearing for their lives. Having narrowly escaped the Pope’s soldiers, they reached Pisa by boat and joined another enemy of John XXII, the Emperor Ludwig of Bavaria. All five were immediately excommunicated.

From 1330 on, Ockham stayed at the Franciscan convent in Munich under the protection of Ludwig of Bavaria and devoted himself to the writing of political treatises. At first, the goal of Michael of Cesena’s supporters was to convince the Christian community that John XXII ought to be deposed. Such was the context for Ockham’s Opus nonaginta dierum (Work of Ninety Days), written in three months in 1332 or 1333, and for the first part of his important unfinished dialogue on the distribution of powers within and outside the church, known simply as the Dialogus. In December 1334, John XXII died. Political discussions were opened between Ludwig of Bavaria and the new Pope, Benedict XII, during which Ockham’s literary activity was brought to a halt. However, no agreement was reached, and from 1337 to 1342 he produced an impressive number of new writings in which he defended more and more explicitly the independence of the imperial and royal powers from those of the Pope. Especially worth mentioning are the Tractatus contra Benedictum (Treatise Against Benedict), the Octo quaestiones de potestate papae (Eight Questions on the Power of the Pope) and treatises 1 and 2 (the only ones extant) of Dialogus III. After another hiatus at the time of Clement VI’s accession to the papal throne, Ockham finally synthetised his political thought in the treatise De Imperatorum et Pontificum potestate (On the Power of Emperors and Popes) in 1346 or 1347. He died in April 1347, a few months before Ludwig of Bavaria. Contrary to an old legend, he had taken no steps toward submitting to the Avignon church.

2 Ontology: antirealism

The core of Ockham’s philosophical system lies in the idea that only individual beings exist and that universals are nothing but signs, spoken, written or mental. This is what has been called his nominalism, a label that came to be associated with his thought towards the end of the fourteenth century (see Nominalism).

The theoretical problem it was intended to solve was provided by Porphyry’s old questions about universals (see Porphyry): do species (such as ‘horse’) and genera (such as ‘animal’) exist by themselves outside the mind or not? Are they corporeal or incorporeal? And are they located in the individual beings or do they exist apart from them? By Ockham’s time, Platonism, identified as the position according to which universals do exist outside the mind as incorporeal beings over and above the individuals that participate in them, had fallen into disrepute (see Platonism, medieval). Aristotle was credited with having definitively refuted it. Most philosophers, then, would follow Thomas Aquinas or John Duns Scotus in adopting some form or other of what we today call ‘moderate realism’, the thesis according to which universals exist outside the mind but only within the individuals that exemplify them. But this, in the eyes of Ockham, was ‘the worst error in philosophy’; and his defence of his own ontology – which he always presented as orthodox Aristotelianism – consisted largely in a detailed, ruthless criticism of the different variants of moderate realism (see Aristotelianism, medieval).

For one thing, he deemed them all incompatible with God’s omnipotence. If the universal ‘horse’ was a common part of each individual horse, then God could not completely destroy any single horse – Bucephalus, for example – without destroying all the others; for in order to destroy the universal ‘horse’ that was part of Bucephalus, God would have to destroy all the other horses as well. This overtly theological argument reveals one of Ockham’s deepest philosophical intuitions: everything that exists, he insisted, should be logically independent of any other thing. This ontological atomism is what he frequently expresses by means of thought experiments involving God’s omnipotence. Since God is credited with the power to do anything which is not self-contradictory – a fundamental theological principle, according to Ockham – the realm of what he can do corresponds to the whole array of logical possibilities, and he should, in particular, be able to destroy any single contingent being while keeping any of the others in existence.

However, Ockham’s main accusation against the varieties of moderate realism he identified among his contemporaries is that in one way or another they all fall short of internal logical consistency. His chief weapon in ontological disputes was the principle of non-contradiction. The best example of this line of attack lies in his famous critique of Duns Scotus’ ‘formal distinction’. Scotus, also a Franciscan, whose work Ockham deeply respected and often discussed at great length, had held that the universal natures such as equinity or animality did have some sort of existence outside the mind, but that they were not in reality distinct from the individuals that exemplified them. They were merely, Scotus contended, formally distinct from them. By this distinction he meant that while they could not exist in reality apart from their individual exemplifications – even by God’s omnipotence – there nevertheless was a ‘foundation in the thing’ for thinking of them as separate. Scotus, like Ockham after him, was dissatisfied with any version of moderate realism that posited the universal nature as being both internal to the individual thing and really distinct from it, because this would entail that the individual thing and the universal nature should logically be able to exist apart from one another, which leads to absurdities. On the other hand, Scotus thought that the validity of the conceptual distinction between the universal and the individual did require that they should not be wholly identical with one another: hence his idea of a formal distinction within real identity.

According to Ockham, this leads directly to contradiction. If the universal nature and the individual thing are really identical to one another, then whatever is true of one of them should also be true of the other, and thus it will be true of the same thing that it is both universal and not universal, individual and not individual. Conversely, if incompatible predicates such as universality and individuality are attributed respectively to the common nature and the individual thing, then this in itself suffices to show that they are distinct from one another in reality, for this is precisely the paradigmatic way of proving that two things are really distinct from one another. Scotus’ formal distinction thus collapses into the real distinction he wanted to reject in the first place. It is easy to see that this argument, like many others Ockham adduces in similar contexts (against Aquinas, for example), makes a crucial use of what we nowadays call the principle of the indiscernibility of identicals: if a and b are identical to one another, then whatever is true of a is true of b; conversely, if something is true of a which is not true of b, then a and b are really distinct from one another.

To avoid an old misunderstanding, it must be stressed that Ockham’s critique of the ontology of universals does not explicitly rely on the methodological principle of economy that Sir William Hamilton, in the nineteenth century, labelled ‘Ockham’s razor’: entities are not to be multiplied without necessity. It is true that Ockham’s thought consistently shows a strong drive towards ontological economy and that he did on many occasions use the razor (which he himself formulated either as ‘a plurality should never be posited without necessity’ or as ‘it is pointless to do with more what can be done with fewer’). However, this principle was commonly accepted before him, even by realist philosophers. It was thought of – by Ockham as well as by others – as a mere methodological rule which, taken by itself, yielded only ‘probable’ conclusions. By contrast, the refutation of the external reality of universals was considered by Ockham as absolutely conclusive since it rested on the principle of non-contradiction.

3 Ontology: substance, quality, form, matter

Although Ockham’s nominalism posits only individual things in the external world, it nevertheless admits of ontological differences among them. First of all, he accepted (for a time) a fundamental difference of status between extramental and mental existence. While universals were refused the former, they were granted the latter. They were thought of, in the first version of Ockham’s Ordinatio, as enjoying a special sort of intentional existence in the mind. This was the existence appropriate to a fictum, a mind-made intelligible object which existed only while consciously produced by the mind as an abstract correlate for acts of intellection, and which, for the duration of its existence, could serve as a natural sign representing certain individual beings. Admittedly, there was no room for this sort of existence within the framework of Aristotle’s ten categories, but Ockham at first explained away this lacuna by restricting Aristotle’s taxonomy to a limited theory of predicates for extramental entities. Later on, however – probably in the early 1320s, under the incisive criticism of his confrère Walter Chatton – Ockham realized that he could achieve an important ontological economy by letting the act of intellection itself play the role of the natural sign. Since internal acts, interpreted as actualized mental potentialities (actus), were commonly classified as qualities of the mind, no special ontological category was needed any longer for intramental existence. The intentional fictum could simply be dropped as soon as one recognized that intellectual acts themselves can serve as semantic contents without any need for internal correlates after all. This is a salient instance of Ockham’s actually using the razor principle: after a period of hesitation, he finally favoured the actus theory over the fictum theory as more probable because it could do with less what the other did with more.

However, even with this simplification, ontology was not utterly stripped of categorial plurality. For one thing, Ockham always maintained a fundamental distinction between substances and qualities. Although he interpreted Aristotle’s theory of the ten categories as a classification of signs rather than things, he would nevertheless acknowledge, corresponding to it, a basic duality amongst individual entities themselves. Substances, whether corporeal or spiritual, were thought of along the Aristotelian line as autonomous beings, while qualities were held to depend upon them for their own existence. Qualities, Ockham would say, ‘inhere’ in the individual substance which displays them. They are not essential parts of it, however, and any one of them can be removed (by natural causes or by God’s omnipotence) without the substance losing its identity. Each substance, on the other hand, has many qualities, simultaneously and successively, and each one has its own: the whiteness of Bucephalus is a particular thing, numerically distinct from Bucephalus itself and from all the whitenesses of any other beings in the world as well, however similar they might be. Ockham endorses particularism with respect to qualities.

Moreover, this nominalistic ontology is further complicated by the incorporation of Aristotelian hylomorphism, the theory of matter and form. Each singular composite corporeal substance is endowed with a variety of internal parts without which it would not be itself: a certain parcel of prime matter on the one hand, and one or more substantial forms on the other hand. Each human being, for example, is a compound of a determinate piece of matter and a number of substantial forms, such as a nutritive form, a sensory form and an intellectual form. Although these partes essentiales are naturally incapable of existing by themselves outside the hylomorphic compound, they are nevertheless counted by Ockham as real, and therefore singular, beings. Matter is thus granted a certain actuality of its own (in opposition to Aquinas). Forms, on the other hand, are stripped of intrinsic generality, each substance having its own.

Ockham, in summary, admits of four basic sorts of singular beings: substances, qualities, substantial forms and pieces of matter. Together they make up a still comparatively simple ontological system, of which singular substances constitute the core, qualities being attached to them as external properties, and forms and matter incorporated as internal parts.

What struck Ockham’s contemporaries in this picture – and many commentators after them – was that it left out not only universals, but relations and quantities as well. These last exclusions, in fact, were a major source of Ockham’s early troubles with religious authorities. The Catholic church was at the time imposing severe pressure on philosophical theories, for fear that philosophers might rule out any of its doctrines as impossible. The doctrines of the Trinity, the Incarnation and the Eucharist in particular, were commonly considered as having important implications for theories about relational connections (such as parenthood or ownership) and quantitative dimensions (such as weight, height or length). Ockham held that neither those connections nor those dimensions had any distinct existence of their own, and this aroused suspicion. However, Ockham had not meant to say that sentences making relational or quantitative claims were neither true nor false, or arbitrarily so. Most of them, he thought, are indeed true or false independently of the human mind: it is not the intellect, for example, that brings it about that Plato is taller or heavier than Socrates. What makes such sentences true or false, Ockham strenuously tried to show, is nothing but substances and qualities themselves. What characterizes a relational or a quantitative sentence, he would typically say, is not the sort of things needed to make it true, but its terms’ modes of signifying. This last point he developed indefatigably and argued for in great detail. To the semantics of quantitative language, in particular he devoted many lengthy passages in his major works, as well as the bulk of two special treatises on the Eucharist, De corpore Christi (On the Body of Christ) and De quantitate (On Quantity), which were obviously written as defences against theological attacks.

4 Epistemology: intuitive and abstractive cognition

Apart from pointing out the inconsistency and imprecision of his opponents, what Ockham had to do in order to accredit his simplified ontology was also to explain as clearly as possible how it fitted with Aristotelian science and with Christian doctrine. For this he had especially to account for the adequacy of knowledge in general. It was a respected Aristotelian adage that science had essentially to do with universals. How could it be salvaged if there are no such universals in reality? Ockham answered the challenge by providing a detailed theory of how mental universals are produced, a theory that was meant as the basis for any validation of conceptual knowledge.

The epistemological process, in this picture, always starts as a direct encounter between singular beings. When a knowing mind equipped with both sensory and intellective substantial forms is in the presence of a perceptible singular object such as a table or a horse, a causal chain naturally ensues, according to Ockham. First, there occurs an apprehension, or intuition, within the sensitive part of the mind. This in turn, together with the object itself, causes certain actual states, or actus, in the intellectual part, states which Ockham labels ‘intellectual intuitions’. These are characterized by the fact that they naturally elicit within the intellect true contingent beliefs about the world, especially judgments regarding existence or non-existence. If Socrates has the right relation to Bucephalus (perceiving it from the right distance, awake, sane and so on), there naturally takes place within Socrates a simple intellectual act, his ‘intuitive cognition’ of Bucephalus, which in turn causes his judgments that Bucephalus exists, is white, is standing there and so on.

Such judgments, of course, even though they are singular, require the availability of certain general concepts such as those of whiteness and existence. These, in Ockham’s view, are also brought about by the same concrete intuitions through an equally natural course. Every time Socrates forms an intuitive act caused by a certain individual in the world, there occur within Socrates’ mind other derivative simple intellectual acts, called abstractive cognitions. These new acts in themselves will not induce empirical judgments of existence; and for that reason they are said to ‘abstract’ from existence and non-existence. However, in virtue of a certain isomorphism (similitudo) they have with the original external thing, they may be used by the mind to represent or stand for this very same thing in its absence, and for any others as well that resemble it sufficiently for the same isomorphism to hold. General signs are thus naturally generated, either as mind-made objects of abstractive acts (according to the fictum theory) or as abstractive acts themselves (according to the actus theory). In either case, the result is what Ockham calls the mind’s concepts (conceptus or intentiones). General concepts, for him, are always causally derivative: ‘every naturally acquired abstractive cognition of a thing presupposes an intuitive cognition of the same thing’ (Ordinatio).

Intellectual intuitions and abstractive concepts, then, are simple mental terms or signs, each naturally representing one or more singular beings in the world. Once produced, these simple terms can be combined with each other, by natural causes or by the will of their possessors, to form cognitive complexes, such as mental propositions. A mental proposition is a structured sequence of mental terms that is either true or false with respect to the singular beings that are referred to by its terms. Such a propositional complex is formed by an intellect’s composite act of apprehension (actus apprehensivus). In the fictum theory, Ockham saw the mental proposition as the intentional correlate of this complex apprehensive act, but later he simply identified the two in the actus theory. Once the mind apprehends a proposition, it can go further and commit itself with respect to its truth or falsity; this is the act of assent, the judgment (actus judicativus). Mental propositions, finally, can be compounded with each other in chains of reasonings, theoretical or practical.

The detailed theory of exactly which structural features and relations with the world render a mental proposition true or false was part of logic for Ockham (see §7 below). Supposing that this semantical part of the programme can be achieved, the general picture we have of knowledge in Ockham’s final theory is that of a natural causal process, involving, apart from external objects themselves, only real qualities of the mind, and leading in stages from intuitive encounters with external singular beings to judgments and inferences involving complex propositional contents, each basic signifying unit in the process being a singular act of a singular mind. There is no longer any such thing as the concept ‘horse’, for example; only token concepts exist. Every mind forms its own single, momentary intellectual acts, which owe their generality, if any, to their signification rather than to a special mode of existence: ‘Nothing is universal save by signification’ (Summa logicae I, 14).

Such mental tokens normally will not subsist very long, but they leave traces when they disappear. We keep intellectual memories of them. Abstractive acts, Ockham contends, causally generate within the mind certain corresponding dispositions (habitus) to form similar acts in the future, and these cognitive dispositions are themselves identified with real qualities of the mind. Thus a general concept comes to be available to a particular mind for future use. When Socrates met Bucephalus, there naturally occurred within Socrates an intellectual intuitive cognition of Bucephalus; and then, as a causal result of this, abstractive cognitions were also produced, which turned out to be capable of simultaneously representing all beings in the world that are sufficiently similar to Bucephalus. In this way Socrates acquires the concept of a horse, the concept of a white thing and so on. Once formed, these general concepts elicit in turn mental dispositions within Socrates to produce replicas of them under appropriate circumstances, new mental tokens representing all horses or all white things, just as the original acts did.

Accordingly, sciences – organized bodies of knowledge – are described by Ockham as ‘collections of intellectual habitus’ in the mind of particular knowers. To say of someone that they have a certain science – that of grammar, for example – is to say that they have internalized, as real qualities of their mind, a certain collection of intellectual dispositions which enable them to form general propositions of grammar when required and which adequately incline them to assent with certainty to those which are true: sciences are ultimately made up of apprehensive and judicative psychological dispositions. Ockham has often been taken to task for having taught that the objects of a science, like the objects of all knowledge or belief, are mental propositions rather than things themselves; but by this he only meant that mental propositions – corresponding to complex apprehensive acts – are precisely what knowers are inclined to assent to by the sciences they have internalized. The contents of knowledge are thus seen as sequences of mental propositions, of which certain terms naturally signify certain singular beings in the world. Thought is mental discourse.

5 Epistemology: direct realism

Ockhamism has often been suspected of leading to radical scepticism in epistemology. If general concepts represent nothing but independent individual things, how can such groupings fail to be arbitrary or misleading? But radical scepticism was, in fact, very far from Ockham’s intentions and spirit, and his theory of universals and knowledge has been more accurately characterized by the best commentators as ‘realistic conceptualism’ (Boehner 1958) or ‘direct realism’ (Adams 1987) (see Epistemology, history of).

For one thing, as was seen in the previous section, the process of concept formation is completely natural. It is the same in every human being and leaves no room for idiosyncratic vagaries. Secondly – and most importantly – this naturally acquired stock of concepts does cut the world at its joints, according to Ockham. Species and genera, of course, are denied any outside reality as distinct beings, but Ockham readily grants that whether an individual thing is or is not of the same species or of the same genus as another is not for the human mind to decide. The conditions of being in the same genus or of the same species are not subjective or arbitrary. They are determined, on the contrary, by what the individual things are in themselves and how they in fact stand to each other. Whether something resembles Bucephalus enough to be naturally represented by the same general concepts does not, Ockham insists, depend upon the human mental apparatus at all. It simply is a rock-bottom fact of the universe. Concept formation, being a natural process, derivatively mirrors the natural distribution of causal powers among individual things, which powers depend in turn on real singular essences and qualities. In this lies the adequacy of abstractive cognition.

Different kinds of accurate, simple, general concepts are thus formed on the basis of direct experience, according to this theory. First, there are more or less general substantial concepts, such as ‘horse’ or ‘animal’, which are identified with species and genera and which are taken to represent in the mind certain groups of individual substances essentially similar to each other independently of their qualities. Second, there are concepts such as ‘whiteness’ or ‘colour’, which represent immediately perceptible singular qualities of substances but not substances themselves. Third, there is another sort of qualitative concepts, such as ‘white’ or ‘coloured’, which represent substances – white things or coloured things in the chosen examples – insofar as they possess certain perceptible qualities. Finally, there are some elementary relational concepts such as ‘darker’ or ‘taller’, which represent individual beings – substances or qualities – insofar as they are related to some others in certain perceptible ways. The first two groups are called ‘absolute concepts’, while the last two are classified among ‘connotative concepts’ (see §6), but all of these are simple mental terms naturally generated as causal results of empirical encounters with singular objects, without any combinatorial activity from the intellect. Together, they are held to provide an adequate basis for knowledge.

Is this empiricism? It would appear so, insofar as it holds that the formation of simple representative concepts in human minds is always triggered by direct singular experiences (of external objects or of mental states themselves). However, it must be stressed that the cognitive process described by the theory presupposes a very strong innate apparatus of rational capacities. A well-formed basic species-concept such as ‘horse’, for example, is automatically generated, according to Ockham, as the result of a single encounter with a horse. More general genus-concepts such as ‘animal’ are formed, in turn, as the results of a minimal number of encounters with individuals of different species. Moreover, certain true contingent beliefs, such as ‘a horse exists’ or ‘this horse is larger than this dog’ are naturally triggered in the mind, as has been seen, as the results of causal processes which also involve highly determinate mental machinery. Certain universal truths are even supposed to be immediately known as such by the mind once the relevant concepts are made available to it, for example, that all horses are animals. The mind, according to Ockham, is equipped from the start with a rich apparatus of cognitive capacities which enable it, under the right circumstances, to reach true scientific knowledge.

One independent reason for linking Ockhamism with scepticism has sometimes been found in its acceptance of the possibility of an intuitive or pseudo-intuitive cognition of nonexistent beings (see Scepticism). However, two different theses must be distinguished in this respect, and neither of them, in Ockham’s view, leads to radical scepticism. First, Ockham did admit the theoretical possibility of an intuitive cognition of nonexistent beings, realizable only, he thought, by the supernatural intervention of God. Since an intuitive act is a real quality of the mind, he reasoned, it is itself a singular being distinct from its own external object; and hence, it is not self-contradictory that it should exist without the object. If this is not self-contradictory, then God can induce in a prophet’s mind, for example, a certain singular cognition of a presently nonexistent being, in virtue of which the prophet would know that this particular being – a future one, or even a merely possible one – does not presently exist, but that it will exist in the future or that it would exist under appropriate circumstances. This singular cognition would then be an adequate intuitive cognition since it would cause within the prophet’s mind true existential judgments about the thing in question. Accordingly, there is no hold for scepticism here: such a supernaturally induced intuition, although abnormal, would not be misleading.

The second possibility seems more disturbing. Ockham admits, since this is not self-contradictory either, that God could directly cause in any human being the false belief that there is a horse in front of them while in fact there is none. Strictly speaking, this would not be an intuitive cognition (it would not cause a true judgment of existence or non-existence), but it could certainly be an undetectable source of error. Such a possibility, however, does not belong to the range of natural processes; and, although it cannot be ruled out by the theory, it can in practice be disregarded by the epistemologist who wishes to assess the scope of natural knowledge. In the normal course of things, intuitive cognition is a totally reliable starting point for science.

6 Logic and philosophy of language: levels of discourse, connotation, intentions

Once concepts are available as natural signs, mental propositions can be assembled. Their truth and falsity will depend upon the semantical properties of their component terms and their syntactical arrangements. Thought is seen as an internal discourse with a compositional structure very similar to that of spoken sentences. Ockham took the ancient idea of mental discourse (found in Boethius, for example) more seriously than any other philosopher before him, and his logic systematically exploits, for the analysis of mental propositions and inferences, the theory of the properties of terms (proprietates terminorum) to which he had been introduced as a student. This theory was an original medieval contribution, which had been progressively developed since the twelfth century by a host of logicians such as Peter of Spain and William of Sherwood, for the analysis of spoken sentences. Ockham adapted it to his nominalistic ontology on the one hand, and enlisted its rich apparatus of concepts and distinctions on the other hand – the theory of suppositio in particular – in the service of a fine-grained understanding of mental computation. This is to a large extent what his logic is about (see Logic, medieval).

At the very outset of Summa logicae, Ockham states that there are three levels of propositions: spoken, written and mental. Those of the first two groups, he says, are composed of publicly perceptible signs, visible or audible; but mental propositions are sequences of concepts – or intentions of the mind – existing only in the privacy of the intellect. Each proposition is composed of terms, and the basic semantical property in this picture is the signification (significatio) of the component terms. The signification of a concept is natural, as has been seen, and that of the other two sorts of terms is conventionally derived from it: spoken terms are conventionally subordinated to concepts, and written terms are conventionally subordinated to spoken ones. A spoken or written term inherits the signification of the previously existing sign to which it is subordinated. When the Latin spoken word ‘equus’, for example, is conventionally subordinated to the mental concept ‘horse’, it thereby acquires the signification that belonged to that concept naturally; and the very same signification is afterwards transmitted in the same way to the corresponding written term. Ockham, then, refuses to say – as did Boethius and Aquinas, among others – that a spoken word signifies the underlying concept. It will instead be said to signify conventionally the individual things themselves that the concept was a natural sign of in the first place: real singular horses in the case of the spoken words ‘horse’, ‘cheval’ or ‘equus’, for example. The same will hold, mutatis mutandis, for the corresponding written words.

At each of the three levels, many distinctions are to be drawn among terms with respect to their signification. First, categorematic terms are distinguished from syncategorematic ones by the fact that they do have a signification of their own before being combined with others into propositions. Proper names such as ‘Socrates’ and common nouns or adjectives such as ‘horse’ or ‘white’ are salient examples of categorematic terms. Syncategoremata, on the contrary, are particles such as prepositions, logical connectives and quantifiers, which do not when taken alone direct the mind towards particular individual beings in the world. Their semantical roles are ancillary: they do not signify anything by themselves but, when combined with categorematic terms, they can affect the modes of reference of those terms and determine the truth-conditions of propositions.

Another important distinction found in mental language as well as in spoken and written discourse, according to Ockham, is between absolute and connotative terms. The former correspond to what we today call natural kind terms, such as ‘horse’ or ‘animal’. These are characterized by the fact that they simultaneously and equally signify all the individuals they are true of, and nothing else: ‘horse’ signifies all horses and nothing but horses. Each connotative term, on the other hand, has at least two different groups of significates: its primary significates are the individuals the term is true of; and its secondary significates are individuals also called to mind by the term, but in an ‘oblique’ way. ‘White’, for example, is a salient case of a connotative term: it primarily signifies all white things and secondarily signifies – or connotes – their whitenesses; although it cannot be said that whitenesses are white, they are nevertheless obliquely called to mind by the term ‘white’. All relational terms, Ockham insists, are connotative: ‘owner’ primarily signifies all owners and connotes their possessions, ‘father’ primarily signifies the fathers and connotes their children, and so on. This idea of connotation thus turns out to be a crucial device for the simplification of ontology. All significates, whether primary or secondary, are singular substances or qualities, and nothing else. Relations, in particular, are no longer needed among real beings. The relevant complexity, here, is located in the semantical structure of certain terms rather than in the ontology.

Finally, some terms signify nonlinguistic things, while others signify signs. When restricted to mental terms, this idea is cashed out, in Ockham’s vocabulary, as a distinction between ‘first and second intentions’. First intentions are mental terms, the significates of which are external beings. Aristotle’s theory of the ten categories is precisely interpreted in this framework as a classification of first intentions according to their modes of signification: the category of relation, for example, is identified with the group of relational first intentions such as ‘owner’ or ‘mother’, the category of quality with that of qualitative first intentions such as ‘white’ or ‘whiteness’, and so on. Second intentions, on the other hand, are concepts signifying concepts. Philosophically, in Ockham’s eyes, the most interesting instances of these are the mental terms ‘species’ and ‘genus’ themselves. ‘Species’ is seen as a metalinguistic concept signifying certain general terms such as ‘horse’ or ‘dog’, while ‘genus’ amounts to approximately the same except that it signifies terms even more general, such as ‘animal’ or ‘flower’. This is exactly what realism about universals crucially misses: it fails to see that concepts referring to universals are fundamentally metalinguistic (see Language, medieval theories of).

7 Logic and philosophy of language: supposition and inference

Signification, then, in Ockham’s logic, is a pre-propositional property of categorematic terms taken in themselves. When such a term, whether spoken, written or mental, is inserted into a proposition as subject or predicate, it is said to acquire a new semantical property called supposition, which is derivative with respect to its signification but which, contrary to signification, can vary from one proposition to another according to contextual factors. Supposition, in modern terms, is the referential function fulfilled by the term in a given propositional context: for a term to ‘supposit for’ certain things, Ockham says, is just for it to stand for these things in a given proposition.

Normally a subject or predicate term supposits for its primary significates. It is then said to be taken in personal supposition (suppositio personalis): in ‘some horses are white’, for example, the subject term ‘horse’ personally supposits for – or refers to – all horses, whether white or not, while the predicate term ‘white’ personally supposits for all white things (but not for whitenesses, which are its secondary significates). Special cases can occur, however: in a sentence such as ‘horse is a five-letter word’, the subject term ‘horse’ does not stand for its primary significates – real horses – but for written tokens of the English word ‘horse’. When a term thus supposits for spoken or written tokens of itself, it is said to be taken in material supposition (suppositio materialis). When it stands for tokens of the corresponding mental sign, such as ‘horse’ in ‘horse is a concept’, it is said to be taken in simple supposition (suppositio simplex). This last case is especially important in Ockham’s discussion of the problem of universals, since the subject terms of sentences such as ‘horse is a species’ or ‘animal is a genus’ are typically considered by him as being taken in simple supposition, and interpreted accordingly as referring in a special way to mental tokens rather than to mysterious external entities such as equinity or animality.

Which individual beings a term refers to in a certain propositional context is thus determined in the first place by the signification of the term and by whether it is taken in personal, simple or material supposition. However, this is still incomplete. It is also determined, Ockham insists, by the tense and the modality of the main verb in the proposition, according to precise rules. A present-tense verb, in particular, is said to restrict both the subject and the predicate of the proposition to supposit for individual beings which exist at the time of utterance. A past-tense verb restricts the predicate to supposit for past individuals, but allows the subject to supposit both for past individuals and for individuals existing at the time of utterance, and so on.

In this way, propositions are linked to reality. Discourse, whether spoken, written or mental, refers to nothing but singular entities, some of which are themselves significant tokens, and it does so through the referential functions of the terms in specific contexts. Propositions considered as complex semantical units do not, according to this view, signify special entities over and above the supposita of their terms. Their peculiarity instead is to have truth-conditions, a detailed theory of which Ockham gives in the second part of his Summa logicae. For elementary statements of the form ‘subject + copula + predicate’, these truth-conditions are entirely formulated in terms of relations between the supposition of the subject-term and that of the predicate. For the truth of a universal affirmative proposition, for example, it is both necessary and sufficient that the predicate supposits for all the individuals the subject supposits for. Similarly, the truth of a universal negative proposition requires that the predicate have no common supposita with the subject, and so on. The theory gets more complicated when it reaches modal propositions, non-elementary propositions (such as conjunctions, disjunctions or conditionals) or other difficult cases such as propositions involving special verbs like ‘cease’ or ‘begin’, which fascinated logicians in the fourteenth century. However, the basis is always provided by the referential link established through supposition between the terms in the proposition and the singular beings out there in the world.

The same is true generally of Ockham’s theory of inferences developed in the very long third part of Summa logicae. This is not formal logic in the modern sense. The validity of inferences is always made to rest in the last analysis upon the referential properties of the component terms. Syllogisms, notably, are described as special arrangements of terms, and their validity is said to depend on the connections between the purported suppositions of the major, the minor and the middle terms. The whole syllogistic theory, in Ockham’s view, ultimately rests, directly or indirectly, on only two relevant connections between terms: the dici de omni (being said of all) and the dici de nullo (being said of none). The former holds when a certain term A supposits for everything another term B supposits for, and the latter when A supposits for none of the supposita of B. ‘All horses are mammals, all mammals are animals, therefore all horses are animals’, for example, is based on the transitivity of the dici de omni. ‘No stone is an animal, all horses are animals, therefore no horse is a stone’ is based on an interplay between the dici de omni and the dici de nullo. All other syllogistic figures are reduced in one way or another to these two connections. In the same vein, nonsyllogistic inferences – which had come to be a major new field of interest in medieval logic under the heading of consequentiae – are also systematically analysed by Ockham as depending upon interconnections between the suppositions of terms. This is how he is led to accept the soundness of such direct inferences as ‘all animals run, therefore all horses run’ or ‘no material body exists, therefore no white thing exists’, the key to which lies not in the formal structure, but in the semantical relations between terms, and ultimately on their reference to singular beings (see Language, medieval theories of; Logic, medieval).

8 Physics

The objects of science for Ockham, as was seen in §4, were universal mental propositions. This controversial thesis, however, did not lead him anywhere near idealism or scepticism, precisely because the supposition of terms was called upon to secure the required links between such mental propositions and real external individual beings. Natural science in particular was recognized as adequate general knowledge of sensible substances. Ockham in fact devoted several treatises to it, the most important of which are his unfinished Expositio in libros Physicorum Aristotelis, his Summa philosophiae naturalis (Synopsis of Natural Philosophy) and his Quaestiones in libros Physicorum Aristotelis (Questions on the Physics of Aristotle). Taken together, these three works occupy more than 2,000 pages in the Franciscan Institute edition and contain some of Ockham’s most intriguing ideas.

The main goal of natural philosophy, as Ockham sees it, is to provide a theory of the general principles of change among sensible things. Following Aristotle, Ockham acknowledges different types of change in nature: generation and corruption of substances, intensification and diminution of qualities, rarefaction and condensation of matter and, finally, local motion. About each one of these he has detailed – and often provocative – positions to defend. However, in the last analysis all change is accounted for in his system on the sole basis of the four kinds of beings admitted by his ontology: substances, qualities, substantial forms and prime matter. Much of his natural philosophy is accordingly devoted to showing that space, void, time, motion and the like are not distinct, absolute things. Prime matter in particular is considered as being actually extended by itself, and its spatial dimensions are not – as in Aquinas and many other medieval authors – given the status of special quantitative forms enjoying an existence of their own.

The core of the method in this peculiar variety of physics is neither empirical nor mathematical but semantical, the point being to show that general sentences which appear to be about space, void, time or motion are in fact about substances, qualities, forms and pieces of matter. Thus reinterpreted, such sentences can very well convey truths, even necessary truths, about physical reality. The crucial device for this type of reductive analysis is the idea that a single word in spoken or written language, such as ‘motion’ or ‘time’, is often an abbreviation for a complex mental expression including not only absolute categorematic terms, but also conjunctions, adverbs, verbs and, above all, connotative terms. Moreover, these abbreviative words are often to be interpreted contextually – for example, the analyst should not systematically try to replace the relevant word by one and the same definition in all its occurrences, but should instead try to reformulate, on the basis of a few rules of thumb, the whole sentences in which the problematic word occurs.

An abstract noun such as ‘change’ (mutatio), for example, does not designate a special entity of its own. Rather, its uses are derivative with respect to those of the corresponding verb ‘to change’ (mutare). The meaning of the verb in such a case provides the key for the interpretation of the various sentences in which the derivative noun occurs. The verb ‘to change’ in effect normally applies to something (for example, a substance) acquiring something which it did not have before (for example, a new form or a new quality) or entering into relations with new things (for example, new substances). This is what should be kept in mind when considering spoken or written sentences involving the derivative noun, such as ‘every change is by an agent’ (which is to be interpreted as ‘everything that changes is changed by an agent’) or ‘change moves from the prior to the posterior’ (which means that ‘when something changes, it moves from a prior state to a posterior state’). The term ‘motion’, in the same vein, normally supposits for the things which are moved, but it may also, if the context favours it, supposit for the things that cause the others to move; or it may even in special cases receive a metalinguistic interpretation and supposit for linguistic or conceptual units such as the verb ‘to move’. The word ‘time’, to take a last example, does not signify any special extramental entity either, but supposits, in the sentences in which it occurs, for the very same things the word ‘motion’ would supposit for in similar contexts, and connotes in addition a certain numbering activity of the human soul.

Sentences involving such words, then, can be ‘saved’ without enriching the ontology, and when they are so reinterpreted, it can be admitted that their truth or falsity is neither illusory nor subjective. Nominalism here does not preclude the objectivity, the mind-independence, or even the necessity of physical phenomena. Ockham in particular is no precursor of Hume in being suspicious about natural causality. Efficient causality in his view is a natural necessary connection holding between singular causes and singular effects in virtue of their respective intrinsic natures; and it can be safely ascertained as such in appropriate circumstances. Ockham readily grants a causal version of the principle of the uniformity of Nature: ‘causes of the same kind have effects of the same kind’ (Ordinatio, prologue, q. 1). The fact that a certain individual A is, in virtue of its intrinsic substantial forms, of the same species as another individual B necessarily implies a strong similarity between A and B with respect to their causal powers. This is true to such an extent that a single observation, in appropriate circumstances, suffices in principle to justify an induction about causal connections: if it could be safely established in a single case that a given singular plant has a certain curative power, it could be correctly concluded by induction that all plants of the same species as this one do have similar curative powers. In conformity with the Aristotelian model, natural philosophy in Ockham’s view is an authentic science of necessary connections. Although the ontology is simplified with the help of sophisticated semantical analysis, traditional metaphysics is not abandoned (see Natural philosophy, medieval).

9 Natural theology

Theology, on the contrary, is not in the normal course of things properly called a science, according to Ockham, because it does not rest on the required sort of natural evidence. In his view a science, strictly speaking, is a set of cognitive habitus (see §4) having to do with necessary conclusions that were formerly dubitable for the agent but that became ascertained through syllogistic reasoning from self-evident general premises or well-established empirical generalizations. It is not so with theology, most of which rests on faith and revelation; the parts that can be demonstrated by natural reason alone are very thin indeed. Compared to most of his medieval predecessors, Ockham is quite sceptical with respect to a purely natural theology (see Natural theology).

First, no simple and proper concept of God, he holds, is accessible to human beings in this life. The human person in this life – frequently called the ‘traveller’ (viator) by medieval theologians – is characterized precisely by the fact of having no direct intuitive cognition of God. However, intuitive cognition of something is a prerequisite condition for the formation of any proper and simple abstract cognition of that thing (see §4), and therefore neither is any such cognition naturally possible in this life with respect to God. The only simple concepts applicable to God that a human being can naturally form are general concepts that will also signify other beings in one way or another. Some will be absolute (or quidditative) concepts (see §6), such as the general concept of ‘being’ which, according to Ockham, univocally applies to God and to creatures. However, most will be connotative or negative terms, such as ‘creator’ (which connotes the creatures) or ‘immortal’ (which negatively signifies death). A proper concept of God, for Ockham, is naturally constructible in this life only as a composite bundle of such general quidditative, connotative and negative concepts.

In the second place, even if some general or composite concepts applicable to God can naturally be formed, this will not suffice for the ‘traveller’ to know that these concepts apply to the Supreme Being. What would have to be known in addition is at least that such a being exists. One can easily form, for instance, the concept of an immortal being, simply by negatively referring to death, but this possibility in itself does not suffice to warrant the belief that such a concept does apply to anything real.

Can the existence of God be proven by natural reason? Ockham criticizes and rejects most of the alleged proofs of his predecessors. Anselm’s celebrated argument, for one, is considered by him as valid only insofar as it proves that among actually existing entities there is at least one with respect to which none is greater (see Anselm of Canterbury). This is far from enough, in Ockham’s eyes, to conclude that nothing could possibly be greater, if it existed. Consequently, the argument does not establish that the greatest possible being does exist in fact. Proofs from final causality, such as Aquinas’ fifth way, do not work either because, Ockham says, it cannot be demonstrated that material things that lack cognition do act according to final causes pre-established by a will (see God, arguments for the existence of).

The proofs of God’s existence that Ockham considers strongest are the arguments from efficient causality. However, these are not all equally conclusive, and even in the best cases they do not prove as much as most of his predecessors would have hoped for. Ockham admits as a self-evident principle that being cannot come from non-being, and concludes accordingly that every natural thing does indeed need to have been brought into existence by some external cause. But nothing, he adds, impedes in principle the possibility of an infinite regress in time in the series of such productive causes. Since no actual infinity would be involved, the past eternity of the material world is not philosophically impossible. What Ockham does deem impossible, on the other hand, is the existence of an actual infinity of simultaneous conserving causes; and this is the basis for the only relevant scientific proof he is ready to grant on this subject. Each caused thing, he believes, needs not only to be brought into existence, but also to be conserved in existence by some external cause (see Creation and conservation, religious doctrine of). Such a conserving cause must exist simultaneously with its effect as long as the effect exists, and the infinite regress in this case is consequently ruled out in principle since it would entail the existence of an actual infinity of distinct beings. This argument, then, does establish that there actually exists at any moment a first efficient conserving cause. What it does not prove, however, is that there should be only one such cause at any moment and that this cause should be identified with God: a celestial sphere or an angel could do equally well.

A fortiori, none of the other traditionally accepted characteristics of the Supreme Being can be proven by natural reason alone to be actually exemplified. In particular, it cannot be philosophically demonstrated, Ockham argues, that God is the first efficient cause of everything, that he is the final cause of something, that he is infinite or even that he knows anything. Articles of faith about God are not in general a matter for reason to settle. Rational argumentation is not ruled out of theology, of course – far from it – but its most crucial premises are accepted solely on the basis of religious faith. Some of the theological truths indeed even run counter to what natural reason by itself would favour: Ockham admits, for instance, that the doctrine of the Trinity involves the actual existence of distinct relational entities, something which, as a philosopher, he firmly rejects. In such cases, Ockham always clearly asserts the priority of the authority of the church over the pronouncements of reason and experience. Philosophy and theology nevertheless tend to be much less intertwined in his thought than they were in the thought of Aquinas or Scotus, for example.

10 Ethics

Ethics is especially interesting in this regard insofar as it simultaneously displays both the intimate interconnection and the relative independence of the philosophical and the theological outlooks. Ockham devoted no special elaborate treatise to ethics and nowhere systematically collected his views on the matter; but many scattered relevant developments in the commentary on the Sentences, the Quodlibeta septem and the collection known as the Quaestiones variae (Various Questions) do reveal, when considered together, an original two-sided theory of the object and foundations of moral knowledge (see Ethics).

Taken as a whole, moral science in this view is the practical normative knowledge of what is to be done, in general or under particular circumstances. It includes two distinct and independent parts. Positive moral science, on the one hand, is knowledge about the legal obligations one is formally subject to; it subdivides in turn into knowledge about human laws and knowledge about divine laws. Non-positive moral science, on the other hand, is directive knowledge about human action (or praxis) insofar as it is based on natural reason and experience. The former, says Ockham, is not a demonstrative science properly speaking, since it depends on human and divine precepts which are not evidently known per se or empirically. The latter, which corresponds to what Aristotle discusses in his own ethical books, is indeed a proper part of demonstrative philosophy, and it is even more certain and useful, Ockham insists, than many other sciences. It rests jointly on natural experience and on a number of general principles evidently known per se, such as: ‘what is honest should be done and what is dishonest avoided’, ‘benefactors deserve gratitude’, ‘the will should conform to the dictates of right reason’, and so on.

The philosophical part of ethics will shed light, in particular, on the general criteria of what is humanly laudable or blameworthy, even for a pagan. Ockham’s theses on this are characteristic. Only acts, according to him, can be morally good or virtuous; and among acts, only internal acts of the will can be rightly considered as intrinsically virtuous. Other sorts of acts, whether bodily or mental, are sometimes called ‘virtuous’, of course, but this is only ‘by extrinsic denomination’, exactly as a beverage is sometimes called ‘healthy’ not because it is itself in good health but because it has some salient causal relation with something else which is (or could be) intrinsically in good health. Ockham’s ethics, like Abelard’s, consistently stresses the basic moral character of intentions rather than that of outward behaviour (see Abelard, P.). His point is that for an act to be intrinsically virtuous, some necessary conditions need to be met that can be fulfilled only by internal acts of the will. First, it has to be free of internal necessity or external compulsion; it has, in other words, to be under the direct power of the will itself. Second, it has to conform to the dictates of what he repeatedly calls ‘right reason’ (recta ratio), which is the rational and well-informed use of prudence and moral conscience.

This notion of ‘right reason’ is central to Ockham’s philosophical ethics. The highest degree of moral virtue pagans can reach, according to him, precisely requires that they should will not merely to fulfil their moral obligations, but also that they should so will precisely in view of the fact that these obligations are dictated by right reason. Right reason, on the other hand, does not reduce to natural reason alone. It involves correct and prudential reasoning enlightened by whatever relevant true knowledge is available to the agent. In the case of the Christian believer, then, the dictates of right reason cannot be independent of the content of Christian faith. This is the exact point where non-positive moral demonstrative science yields, for Ockham, to a higher form of ethics: positive Christian moral science, as enlightened by religious faith.

This is not to say that philosophical moral science by itself is completely unreligious. Ockham explicitly holds, on the contrary, that reason suffices to demonstrate that there is at any time an actually existing summum bonum, and right reason, then, dictates, independently of any divine revelation, that nothing else ought to be loved more than this summum bonum. However, Christian revelation goes much further. It tells the believer, among other things, that this summum bonum is the unique God, that he is not only the highest good in fact, but also the highest possible good, that he is our creator and benefactor, that he is a personal knower and so on. Once these data from revelation are taken into account, right reason should lead the believer towards an even higher degree of moral virtue, which will correspond to Christian morality proper. It is reached when agents will to fulfil their obligations not merely because they conform to the dictates of right reason anymore, but primarily for the love of God himself and because these obligations derive from God’s will. This alone is the level of perfect moral virtue.

The real ultimate foundation of ethical norms, then, turns out to be God’s will and nothing else. The sole fact that God commands something to be done is what makes that thing morally good. God could at any time change his precepts and our moral obligations would then change accordingly. He could command, for example, that we should from now on steal whenever we can and it would ipso facto become morally good to do so. However, this is no longer demonstrative ethics; it is Christian theology based on revelation and on the indemonstrable principle of God’s absolute supremacy. Even though religious faith leads him beyond philosophical ethics into what has often been called a ‘divine command ethics’, which ultimately plays a foundational role in his overall system, Ockham in the last analysis does not blur the distinction he had drawn between the two sorts of moral knowledge, and he never expresses serious doubts about the soundness of secular moral reasoning in the actual world.

11 Political thought

While Ockham had not ventured into political philosophy during his academic career in England, almost all the works he is taken to have written in Munich from 1330 to his death in 1347 are directly related to his conflicts with the Avignon papacy (with the possible exception of one short logical tract, the Elementarium logicae (Elements of Logic)). His goal at first was to expose the errors and heresies of Pope John XXII, especially about poverty within the church and about the beatific vision. This raised in effect the delicate question of papal heresy: who, in such a case, is entitled to denounce it? Who has the power to depose the Pope? Reflections on such matters progressively led Ockham to be more and more interested in political theory proper, and most of his writings after 1337 were directly devoted to it, notably the Octo quaestiones de potestate papae, Book III of the Dialogus and the De Imperatorum et Pontificum potestate.

In this endeavour, Ockham primarily thought of himself as a theologian. Many of his arguments against the Avignon curialists were designed for the ecclesiastical community and based on the Bible, the writings of the Church Fathers or canon law. However, he also liberally used Aristotle’s Politics and much of his thought in this field can be seen, in fact, as being in direct continuation with his philosophical ethics of right reason: politics, after all, is but a province of human praxis.

Indeed, Ockham’s basic political idea is that the spiritual and the temporal powers should normally be kept apart and not be allowed to overlap, except in special cases of crisis such as papal heresy or tyrannical abuse. On the whole, he found much to say in favour of the institution of papacy, but he energetically opposed the papalist doctrine of the plenitudo potestatis of the Pope and emphatically denied the dependence in principle of secular on ecclesiastical power. The church, he thought, should as a general rule disentangle itself from worldly politics. Consecration by the Pope, for example, was not in his view a necessary condition for the legitimacy of the Emperor.

What then is the basis for the legitimacy of secular political power? Popular consent, according to Ockham, is the normal original source of legitimacy; but beyond this, the rightness of a certain political regime ultimately depends on how well it fulfils its functions. Government is instituted for the good of a community of individual subjects, and if a regime adequately performs this task, it is not legitimate, for the Pope or even for the majority of subjects, to try to overthrow it by force. Ockham’s approach to politics is basically functional. What he thinks should be expected from a government is mainly that it should prevent and punish injustice and so preserve in this way the rights and freedom of the individual members of the community. Monarchy, for him, is usually the best regime insofar as it is, in most circumstances, best suited to such a role; but there is nothing absolute – or divinely founded – in this judgment in Ockham’s eyes. A political regime is a man-made institution to be judged by its expediency in achieving the goal for which it should ideally be designed: and common welfare or public security can in principle be enhanced by different regimes in different circumstances.

Natural rights, in this perspective, are what a government is expected to protect (see Rights). Ockham never gave a systematic account of these rights, but examples of them in his writings include the individual’s right to the necessities of life, the collective right for a people lacking a ruler to choose one, the right to resist an unjust government, and so on. As a general rule, the rights and obligations of rulers and subjects, he thought, can be determined in particular circumstances by the normal prudential use of human right reason. Ultimately, what the political and legal institutions should be aiming at preserving is the individual freedom of the members of the community in their own private spheres.

At the same time this respect for freedom sets a limit in principle to the exercise of any political power, whether ecclesiastical or secular: ‘free persons, who are not slaves’, Ockham writes, ‘should never, without some fault, be compelled by new laws to do things which are not necessary to the commonwealth or to their neighbour’ (Breviloquium de potestate Papae II, 17). Political rule should be kept to the minimum which is required in any circumstances for the fulfilment of its social functions.

It has often been wondered whether Ockham’s political thought is dependent on the rest of his philosophy, and on his nominalism in particular. Certainly his political theories were not deduced from nominalistic premises in ontology, theory of knowledge or philosophy of language. He never defended his political stands by arguments drawn from these fields, and his conceptions of ecclesiastical and political power are compatible with different ontological or epistemological doctrines. Moreover, probably because of the new audience he was trying to reach, he did not make much use in his political writings of the technical tools of semantical analysis which he had so extensively exploited in theology and philosophy. Nevertheless, the break between the two parts of his work is far from complete. Ockham’s approach to politics and natural rights is in direct continuation with his philosophical ethics of right reason. And, more importantly, the emphasis of his later writings on personal freedom can certainly be seen as the political counterpart of the accent on singularity which was the trademark of his nominalism. Even though there is no logical connection here, both aspects of Ockham’s thought harmoniously fall in line with each other in consistently stressing the primacy of individuals.