Roberto Grossatesta

Grosseteste, Robert (c.1170–1253)

Grosseteste’s thought is representative of the conflicting currents in the intellectual climate of Europe in the late twelfth and early thirteenth centuries. On the one hand, his commitment to acquiring, understanding and making accessible to his Latin contemporaries the texts and ideas of newly discovered Arabic and Greek intellectual traditions places him in the vanguard of a sweeping movement transforming European thought during his lifetime. His work in science and natural philosophy, for example, is inspired by material newly translated from Arabic sources and by the new Aristotelian natural philosophy, especially the Physics, On the Heavens and Posterior Analytics (Aristotle’s treatise on the nature of scientific knowledge). Similarly, in his work in metaphysics, ethics and theology Grosseteste turns to ancient sources previously unknown (or incompletely known) to Western thinkers, prominent among which are Aristotle’s Ethics and the writings of Pseudo-Dionysius. His work as a translator of and commentator on Aristotle and Pseudo-Dionysius places Grosseteste among the pioneers in the assimilation of these important strands of the Greek intellectual heritage into the mainstream of European thought.

On the other hand, Grosseteste’s views are in significant respects conservative. His greatest debt is to Augustine, and his most original ideas – such as his view that light is a fundamental constituent of all corporeal reality – are extensions of recognizably Augustinian themes. Moreover, although his work on Aristotle is groundbreaking, his approach is judicious and measured, lacking any hint of the crusader’s zeal that marks the work of the later radical Aristotelians. In general his practice conforms to the traditional Neoplatonist line, viewing Aristotle as a guide to logic and natural philosophy while turning to Platonism – in Grosseteste’s case, Augustinian and Pseudo-Dionysian Platonism – for the correct account of the loftier matters of metaphysics and theology.

1 Life and works

Grosseteste was born probably shortly before 1170 in Suffolk, England. There is little evidence of his activities until the mid-1220s, when he would have been already well over fifty years old. In 1225 he was lecturing in theology at Oxford, where he also served for a time as chancellor of the university. In 1230 he left his post in Oxford’s secular schools to become the first lecturer at the newly established house of studies for the Oxford Franciscans. He remained there until 1235 when he was elected bishop of Lincoln, England’s largest diocese, which then included Oxford. He served in that position until his death in 1253.

We know little about Grosseteste’s formal training or career prior to his appearance at Oxford in 1225. He may have begun his studies at Oxford or Cambridge in the 1180s, receiving the degree of Master of Arts by the end of that decade. He seems to have had an administrative career in the household of the Bishop of Hereford until perhaps 1198. It may have been in Hereford, an early centre of interest in scientific speculation, that Grosseteste developed his deep interests in natural philosophy, astronomy and mathematics. His earliest works, dating from about 1200–20, deal with subject matter of this sort: they include De cometis (On Comets), De artibus liberalibus (On the Liberal Arts), De generatione sonorum (On the Generation of Sounds), De sphaera (On the Sphere) and De impressionibus aeris (On the Influences of Air). Shortly after 1220 Grosseteste seems to have begun serious reflection on Aristotle. His Commentarius in Posteriorum analyticorum libros (Commentary on Aristotle’s Posterior Analytics), perhaps the first complete medieval commentary on that text, probably dates to the early 1220s. The earliest of his notes on Aristotle’s Physics (which have been gathered together as the Commentarius in VIII libros Physicorum) may date from the same period. It is unclear whether Grosseteste ever studied at Paris or whether he spent time in Paris during the suspension of studies at Oxford in 1209–14, as many English academics did.

During the 1220s at Oxford, the study and teaching of theology moved to the center of Grosseteste’s attention. As part of his study of the Bible and the Church Fathers, Grosseteste began learning Greek, an undertaking that would yield remarkable fruit in his late-blooming career as a philosophical theologian. The writings in philosophical theology that belong to the period from 1225–30 include De veritate (On Truth), De veritate propositionis (On the Truth of the Proposition), De libero arbitrio (On Free Choice) in two recensions, De scientia Dei (On God’s Knowledge) De statu causarum (On the Finitude of Causal Series), De intelligentiis (On Intelligences) and De unica forma (On the Single Form).

Grosseteste’s growing theological occupations did not displace his work in natural philosophy, however, and in the period from 1225 to about 1240 he continued to write on natural philosophy, weaving together his scientific and mathematical interests with his theological work. He continued to lecture on Aristotle’s Physics into the early 1230s, and composed his treatise on the six days of creation, Hexaemeron, in 1230–5 as well as several treatises on broadly scientific matters, including De impressionibus elementorum (On the Influences of the Elements), De motu supercaelestium (On the Motion of What is Above the Heavens), De motu corporali et luce (On Corporeal Motion and Light), De lineis (On Lines), De natura locorum (On the Nature of Places), De iride (On the Rainbow), De colore (On Colour), De calore solis (On the Heat of the Sun), De operationibus solis (On the Activities of the Sun, an exposition of Ecclesiasticus 43: 1–5), De finitate motus et temporis (On the Finitude of Motion and Time) and De differentiis localibus (On the Differentiae Associated with Place). Central to Grosseteste’s scientific reflections in this period is his developing account of the nature of light and its fundamental role in both natural and divine causality. That account reaches its fullest development in De luce (On Light).

The crowning scholarly achievements from the years in which Grosseteste was Bishop of Lincoln result from monumental projects involving translation of and commentary on Greek philosophical and theological texts. In the mid-1230s he revised a twelfth-century translation of John Damascene’s De fide orthodoxa (On the Orthodox Faith) (see John of Damascus) and produced the first Latin translations of the remainder of Damascene’s corpus, De logica (On Logic), De centum heresibus (On the Hundred Heresies), Elementarium dogmatum (Introduction to Doctrine) and De hymno Trisagion (On the Hymn ‘Holy, Holy, Holy’). Shortly thereafter he began the largest of his scholarly endeavours, the production of translations of and commentaries on each of Pseudo-Dionysius’s four major treatises: De caelesti hierarchia (On the Celestial Hierarchy), De ecclesiastica hierarchica (On the Ecclesiastical Hierarchy), De divinis nominibus (On the Divine Names) and De mystica theologia (On Mystical Theology) (see Pseudo-Dionysius). By 1243 this massive undertaking was complete, and Grosseteste turned next to Aristotle’s Ethics (see Aristotle). By the late 1240s he had finished the first Latin translation of the complete text of the Ethics. To accompany his translation Grosseteste produced translations of the ancient Greek commentators on the Ethics and his own glosses on the text. Apparently in the last years of his life, at close to eighty years of age, Grosseteste began studying Hebrew.

2 Augustinian psychology and epistemology

Following Augustine, Grosseteste appeals to the nature and behaviour of light to explain the fundamental nature of reality and human cognition of it. God is the first and highest light, and all creatures depend on God in the way rays of light depend on the light source from which they radiate. The eternal ideas in God act as principles in creation (creatrices) insofar as they are the formal exemplar causes of created things. Creatures have their being, and hence are ‘true’ (in the sense of ‘true friend’) to the extent to which they conform or are ‘adequated’ to the eternal ideas.

Grosseteste holds that since the eternal ideas in God are the exemplars of created things, knowledge of creatures depends on illumination from God:

Since the truth of each thing is its conformity to the idea of it in the eternal Word, it is clear that every created truth is seen only in the light of the highest truth.…All created truth, therefore, is clear insofar as the light of its eternal idea is present to the observer, as Augustine testifies. Nor can anything be seen to be true in its created truth alone, just as a body cannot be seen to be coloured solely in its colour apart from the illumination of an extrinsic light.

(De veritate)

Grosseteste believes that our cognitive dependence on God’s illumination is a function of our weakness. Just as the weak eyes of the body cannot look at the sun itself, despite their depending on sunlight for seeing coloured bodies, the weak eyes of the mind cannot look on the highest truth itself, though the mind depends for its vision of truth on the light streaming from it. By contrast, pure intellects – the divine intellect, the separate intelligences and purified human intellects (in heaven) – have knowledge by virtue of their direct awareness of the eternal ideas and of the highest light itself (De veritate; Commentarius in Posteriorum analyticorum libros I.7, I.14).

In Grosseteste’s view, our cognitive weakness is explained in part by the soul’s embodiment:

If the highest part of the human soul – the so-called intellective part which is not the actuality of any body and needs no corporeal instrument for its proper activity – were not clouded and weighed down by the weight of the corrupt body, it would have complete knowledge without the aid of sense-perception through an irradiation received from a higher light, just as it will have when the soul has cast aside the body.… But because the purity of the eye of the soul is clouded and weighed down by the weight of the body, all the powers of the rational soul are oppressed from birth by the weight of the body so that they cannot act, and so are in a certain way drowsy.

(Commentarius in Posteriorum analyticorum libros I.14)

Our embodiment also accounts for the indispensable role sense-perception plays in our acquisition of knowledge: ‘In the course of time, as sense-perception acts through its many encounters with sensible things, reason (which is intermingled with the senses and is, as it were, ferried to sensible things by the senses as in a boat) is awakened’ (Commentarius in Posteriorum analyticorum libros I.14). Once awakened, reason begins to function, drawing distinctions and abstracting until it arrives at cognition first of universals, then of necessary truths and finally of the sorts of demonstrations that provide the strictest kind of knowledge.

Human cognitive weakness results not only from the soul’s embodiment but also from the soul’s misdirected love:

The cause of the soul’s sight’s being clouded through the weight of the corrupt body is that the soul’s affection and vision (affectus et aspectus) are not distinct, and it attains its vision only by that by which it attains its affection or its love. Therefore since the soul’s love and affection are directed toward the body and bodily enticements, it necessarily drags the soul’s vision behind it and directs it away from its light.

(Commentarius in Posteriorum analyticorum libros I.14)

In our present state, turned away from the light, we must make our way toward truth starting from vestiges of light discovered in the external senses; but to the extent that our love is directed away from corruptible things, our cognitive gaze will be directed toward its own light until, purified of bodily distractions, it will look on the light itself.

3 Light as the first corporeal form

Some of Grosseteste’s most original ideas result from his extension of the Augustinian metaphor of illumination to issues in natural philosophy. He is captivated by a particular characteristic of light, namely, its essential ability to multiply and diffuse itself instantaneously (as he thought) in all directions. He saw in this feature the mechanism of an ambitious account of the generation of the physical universe (see Illumination).

The problem, as Grosseteste sees it, is to account for the three-dimensional extension of bodies and of the corporeal universe in general. This is because the ultimate principles of corporeal things are prime matter and bodily form, each of which is in itself simple and utterly dimensionless. Prime matter must be dimensionless because its possessing dimensions would entail its being informed in some way; and bodily form, considered just as form, must be wholly immaterial and cannot therefore be spatially extended. Hence the combination of simple, unformed matter with simple form cannot give rise to quantitative extension. Moreover, no finite multiplication of a simple form in matter can give rise to quantitative extension because no aggregation of a finite number of extensionless entities can constitute anything extended. Grosseteste’s solution to this problem is to identify light with the primary corporeal form:

I judge that the first corporeal form, which some call corporeity, is light. For light, of itself, diffuses itself in every direction so that from a point of light, a sphere of light as great as you please is generated instantaneously.… But corporeity is that from which the extension of matter into three dimensions necessarily follows.… But it was impossible for form, which in itself is simple and dimensionless, to introduce dimensions into matter in every direction – since matter is likewise simple and dimensionless – except by multiplying and diffusing itself instantaneously in every direction and by extending matter, in its diffusion. For form itself could not leave matter behind, since it is not separable.

(De luce)

In its instantaneous infinite multiplication light, as it were, stretches the matter it informs into a three-dimensional quantity. Grosseteste holds that this generation of extended matter occurs instantaneously at the beginning of time when God creates the first corporeal form in prime matter, which God also creates simultaneously. Moreover, he holds that since the infinite multiplication of something simple yields something finite (because what is produced by the infinite multiplication of something infinitely exceeds that by the multiplication of which it was produced), light’s instantaneous infinite multiplication of itself yields finite corporeal extension in every direction. The full extent of that finite extension defines a sphere coextensive with the whole of the corporeal universe (machina mundi).

Grosseteste’s reflections on the generation of the corporeal universe lead him to two particularly interesting corollaries. First, he reasons that if in general the infinite multiplication of something simple is required to produce a thing of finite quantity, then it must be that there are infinities of different magnitudes, the difference in the magnitude of the infinities accounting for the quantitative difference in objects of different sizes:

Now, it is possible that an infinite aggregation of numbers is related to another infinite aggregation in any numeric ratio (and even in any non-numeric ratio), and [so] there are infinities that have more [elements] than other infinities and infinities that have fewer than others. (The aggregation of all the numbers, both even and odd, is infinite, and it is thus greater than the aggregation of all the even numbers, which is nevertheless infinite.) …It is clear therefore that by its infinite multiplication, light extends matter into smaller finite dimensions and into larger finite dimensions in any ratio whatever.

(De luce)

Thus, the first corporeal form – light – explains not only how there can be a three-dimensional corporeal world but also how there can be bodies in it of different sizes.

Second, Grosseteste supposes that since light is the first corporeal form and as such is intrinsic and fundamental to all corporeal reality, understanding the behaviour of light is fundamental to understanding all natural phenomena. Mathematics, therefore, and in particular geometry and optics (the science of refraction), are indispensable tools for natural philosophy: ‘The consideration of lines, angles, and figures is especially useful since it is impossible to have knowledge of natural philosophy without them’ (De lineis). Grosseteste’s lifelong commitment to these disciplines provides the foundation for an enduring tradition of mathematical and scientific speculation at Oxford in the later Middle Ages (see Natural philosophy, medieval; Oxford calculators).