Pierre Gassendi

Gassendi, Pierre (1592–1655)

Pierre Gassendi, a French Catholic priest, introduced the philosophy of the ancient atomist Epicurus into the mainstream of European thought. Like many of his contemporaries in the first half of the seventeenth century, he sought to articulate a new philosophy of nature to replace the Aristotelianism that had traditionally provided foundations for natural philosophy. Before European intellectuals could accept the philosophy of Epicurus, it had to be purged of various heterodox notions. Accordingly, Gassendi modified the philosophy of his ancient model to make it conform to the demands of Christian theology.

Like Epicurus, Gassendi claimed that the physical world consists of indivisible atoms moving in void space. Unlike the ancient atomist, Gassendi argued that there exists only a finite, though very large number of atoms, that these atoms were created by God, and that the resulting world is ruled by divine providence rather than blind chance. In contrast to Epicurus’ materialism, Gassendi enriched his atomism by arguing for the existence of an immaterial, immortal soul. He also believed in the existence of angels and demons. His theology was voluntarist, emphasizing God’s freedom to impose his will on the Creation.

Gassendi’s empiricist theory of knowledge was an outgrowth of his response to scepticism. Accepting the sceptical critique of sensory knowledge, he denied that we can have certain knowledge of the real essences of things. Rather than falling into sceptical despair, however, he argued that we can acquire knowledge of the way things appear to us. This ‘science of appearances’ is based on sensory experience and can only attain probability. It can, none the less, provide knowledge useful for living in the world. Gassendi denied the existence of essences in either the Platonic or Aristotelian sense and numbered himself among the nominalists.

Adopting the hedonistic ethics of Epicurus, which sought to maximize pleasure and minimize pain, Gassendi reinterpreted the concept of pleasure in a distinctly Christian way. He believed that God endowed humans with free will and an innate desire for pleasure. Thus, by utilizing the calculus of pleasure and pain and by exercising their ability to make free choices, they participate in God’s providential plans for the Creation. The greatest pleasure humans can attain is the beatific vision of God after death. Based on his hedonistic ethics, Gassendi’s political philosophy was a theory of social contract, a view which influenced the writings of Hobbes and Locke.

Gassendi was an active participant in the philosophical and natural philosophical communities of his day. He corresponded with Hobbes and Descartes, and conducted experiments on various topics, wrote about astronomy, corresponded with important natural philosophers, and wrote a treatise defending Galileo’s new science of motion. His philosophy was very influential, particularly on the development of British empiricism and liberalism.

1 Life and works

Pierre Gassendi was born in Champtercier, a village near Digne in Provence, France. He received his early education in Digne and Riez and was admitted to the clerical state in 1604. The remainder of his formal education was supervised by the Church, as it formed part of his preparation for the priesthood. From 1604 through 1611 he studied Aristotelian philosophy and Catholic theology at the college of Aix-en-Provence. Upon receiving his doctorate in theology at Avignon in 1614, he was appointed official diocesan teacher of theology and superintendant of theological education. In 1616 he assumed the chair of philosophy at Aix-en-Provence, where he taught Aristotelian philosophy for the next six years. He voiced his dissatisfaction with Aristotelianism in his first published work, Exercitationes Paradoxicae Adversus Aristoteleos (Paradoxical Exercises against the Aristotelians) (1624), in which he claimed to have taught his students the principles of Aristotelianism, only to refute them with sceptical arguments. When the college at Aix was turned over to the Jesuits in 1622, Gassendi and the rest of the faculty were forced to leave their positions. Since his student days, he had been a member canon of the Cathedral of Digne. He was appointed provost of the Cathedral in 1634, a position which he held for the rest of his life.

Apart from his administrative position at the Cathedral of Digne, Gassendi relied on patronage for his scholarly work. His first patron was the polymath and humanist Nicolas-Claude Fabri de Peiresc (1580–1637), councillor of the Parlement of Aix and patron of arts and letters. Gassendi and Peiresc conducted scientific experiments together and corresponded about astronomy and philosophy. During the years until Peiresc’s death, Gassendi divided his time among Aix, Digne, and Paris. During the winter of 1628, he travelled with his friend the libertin érudit François Lullier (c.1600–51) to Holland where he met a number of important intellectual figures, including the atomist Isaac Beeckman (1588–1637), who reinforced his resolve to restore the philosophy of Epicurus, an enterprise that became his life’s work.

In 1630, Gassendi published two works not directly related to his Epicurean project. In the Epistolica exercitatio, in qua principia philosophiae Roberti Fluddi, medici, reteguntur he responded to Marin Mersenne’s request for an evaluation of the natural philosophy of the Paracelsian Robert Fludd (see Mersenne). In the Parhelia, sive soles quat[u]or qui circa verum apparuerunt Romae, die XX mensis martii anno 1629 he gave an account of a strange appearance of parhelia (or the appearance of multiple suns and patches of shimmering light around the sun). Two years later, in Mercurius in sole visus et Venus invisa Parisiis anno 1631, he confirmed Kepler’s prediction of Mercury’s transit of the sun.

Gassendi suffered a major loss when Peiresc died in 1637. Losing not only his patron but also a close and valued friend, he wrote little for the next four years. In 1641 he published a memorial to his friend, Viri illustris Nicolai Fabricii de Peiresc Senatoris Aquisextiensis vita. Having returned to Provence to perform his clerical duties, Gassendi was invited by Louis-Emmanuel de Valois, count of Alais, a man closely connected to the royal family, ‘to wait upon’ him, that is, to enter a client–patron relationship which continued until Valois’ death in 1653.

Gassendi was deeply involved in the major developments in natural philosophy in his day. He published an exposition of Galileo’s new science of motion, De motu impresso a motore translato (1642), which contains the first correct statement of the principle of inertia in print (see Galileo, G.). Prior to the publication of Descartes’ Meditations in 1641, Mersenne invited Gassendi, among other philosophers and theologians, to comment on the manuscript of the work. These comments, first published as the fifth set of ‘Objections’, were enlarged in Gassendi’s Disquisitio metaphysica, seu dubitationes et instantiae adversus Renati Cartesii metaphysicam et responsa (Metaphysical disquisition, or doubts and instances against the metaphysics of René Descartes and responses) (1644), which contains Gassendi’s objections to the Meditations, Descartes’ replies, and Gassendi’s rejoinders (see Descartes, R.). He also published an account of the new astronomy in Institutio astronomica juxta hypotheseis tam veteram quam Copernici et Tychonis Brahei (1647).

In 1645, Gassendi received an appointment as professor of mathematics at the Collège Royal. In 1653, after Valois’ death, Gassendi came under the protection of Henri-Louis Habert, lord of Montmor, a patron of natural philosophy, with whom he lived until his own death in 1655.

During the last decade of his life, Gassendi published the products of his extensive work on the life and philosophy of Epicurus. The three major Epicurean works include De vita et moribus Epicuri libri octo (1647), Animadversiones in decimum librum Diogenis Laertii, qui est de vita, moribus, placitisque Epicuri (Observations on Book X of Diogenes Laertius, Which is about the Life, Morals, and Opinions of Epicurus) (1649), and the Syntagma Philosophicum, published posthumously in 1658.

2 Gassendi’s Epicurean project

The unifying theme of Gassendi’s work was his project to restore the philosophy of Epicurus, making it acceptable to orthodox Christians. He envisaged this Christianized Epicureanism as a complete philosophy that would replace Aristotelianism, which had been dominant in the universities for centuries (see Aristotelianism in the 17th century; Epicurianism).

Gassendi’s rejection of Aristotelianism is the theme of his 1624 Exercitationes Paradoxicae Adversus Aristoteleos. Drawing on the Pyrrhonian scepticism of Sextus Empiricus, Gassendi attacked the epistemological and metaphysical foundations of Aristotelianism (see Pyrronism). He rejected Aristotle’s philosophy of matter and form, as well as his ideal of demonstrative certain knowledge as the epistemological goal of natural philosophy (see Aristotle). Rather than sinking into sceptical despair, however, Gassendi adopted what Popkin (1979) has happily called ‘mitigated scepticism’, advocating a science of appearances which can attain at best probable knowledge of things based on their appearances. He denied the possibility of knowing essences and explicitly allied himself with the nominalists (see Nominalism). An empiricist epistemology and a nominalist metaphysics were central themes in his philosophical writings. In this early work as well as in correspondence from the second half of the 1620s, he expressed a growing interest in Epicureanism as a substitute for Aristotelianism.

Although there is evidence that Gassendi was attracted to the philosophy of Epicurus from the mid-1620s, he did not defend Epicureanism in print until the 1640s. During the intervening years, his Epicurean project grew from the straightforward humanist task of translating Book X of Diogenes Laertius’ Lives of Eminent Philosophers, one of the major sources for knowledge of Epicurus’ writings, to a full-fledged rehabilitation of Epicureanism (see Diogenes Laertius). During the early 1630s, Gassendi produced a manuscript of his Epicurean commentary, which he shared chapter-by-chapter with Peiresc and some other friends. By 1634, he completed a draft of what would later be published as De vita et moribus Epicuri (1647). During 1641 and 1642, he wrote a series of letters containing a sketch of his Epicurean project to his patron, the new governor of Provence, Louis-Emmanuel de Valois. In De vita et moribus Epicuri, Gassendi defended Epicurus against the allegations of decadence and immorality that had dogged his reputation since antiquity. In 1649, he published Animadversiones in decimum librum Diogenis Laertii, a book still conceived in the humanist format as a commentary on an ancient text. The posthumous Syntagma Philosophicum (1658) was the culmination of Gassendi’s Epicurean project, incorporating material from contemporary natural philosophy into an exposition of Epicureanism.

At every stage of his Epicurean project, Gassendi was concerned to modify certain of the ancient philosopher’s doctrines in order to make his philosophy consistent with Christian orthodoxy. He rejected the theologically objectionable components of Epicureanism: polytheism, a corporeal conception of the divine nature, the negation of all providence, the denial of Creation ex nihilo, the infinitude and eternity of atoms and the universe, the plurality of worlds, the attribution of the cause of the world to chance, a materialistic cosmogony, the denial of all finality in biology, and the corporeality and mortality of the human soul. Gassendi replaced these doctrines with a Christianized atomism which asserted the creation of the world and its constituent atoms by a wise and all-powerful God who rules the world providentially, the existence of a large but finite number of atoms in a single world, the evidence of design throughout the Creation, a role for final causes in natural philosophy, and the immortality and immateriality of the human soul.

Gassendi’s theology was thoroughly voluntarist. Voluntarism is an interpretation of God’s relationship to the Creation which insists on God’s omnipotence and his absolute freedom of will. Nothing exists independently of him, and nothing that he creates can bind or impede him. Emphasizing the contingency of the world on God’s will, Gassendi believed that God’s omnipotence is in no way constrained by the Creation, which contains no necessary relations that might limit God’s power or will. ‘There is nothing in the universe that God cannot destroy, nothing that he cannot produce, nothing that he cannot change, even into its opposite qualities’ (1658 vol 1: 308). Consequently there are no universal or eternal essences of created things. Even the laws of nature lack necessity. ‘He is free from the laws of nature, which he constituted by his own free will’ (1658 vol 1: 381). The laws of nature have no existence apart from serving as descriptions of the regularities we observe in the operations of nature. In contrast to Descartes, Gassendi never identified any particular propositions as laws. Like everything else God created, he can negate them. He could have created an entirely different natural order if it had pleased him to do so. Similar to other voluntarists, for example Ockham, Gassendi believed that God’s will was constrained only by the law of non-contradiction and that nothing God creates can prevent him from acting directly on the Creation. God does not directly produce all the motions of bodies, nor does he simply create bodies in the beginning, leaving them to act in accordance with their individual natures as bodies. He makes use of second causes – that is, natural causes that he has created. But he can always intervene and act directly if he wants. Nothing he creates constrains him in any way. ‘God… is the most free; and he is not bound, as he can do whatever… he wishes’ (1658 vol 1: 309). Nominalism was one important implication of Gassendi’s voluntarism. The existence of universals, even universals created by God, would limit God’s freedom of action. Gassendi’s voluntarism and anti-essentialism played a central role in his debate with Descartes over the Meditations. These assumptions infused every part of his version of Epicureanism.

Gassendi employed humanist methods in philosophy. That is, he insisted on finding an ancient model for his philosophical views, and he wrote in a style marked by frequent allusions to and quotations from classical authors. Each section of his massive Syntagma Philosophicum begins with a summary of all existing views on the subject at hand. Only after having rehearsed all the traditional views did he embark on his own account of a subject. He articulated his own views in dialogue with his ancient model, Epicurus. In this respect, he was traditional, even though the content of his philosophy in many ways broke from traditional ideas. He claimed that he chose Epicurus as his model because his atomistic physics and hedonistic ethics could be more readily reconciled with ‘the Sacred Faith’ than any of the other ancient schools of philosophy. Presented as a complete philosophy to replace Aristotelianism, the Syntagma Philosophicum is divided into three large sections, entitled ‘Logic’, ‘Physics’, and ‘Ethics’.

3 Logic

The first part of the Syntagma Philosophicum, entitled ‘Logic’, is the culmination of Gassendi’s lifelong considerations of this subject. He proposed to substitute the canonic of Epicurus for Aristotelian dialectic which he judged to be useless for obtaining knowledge of nature. He considered logic to be the art of thinking well. He developed it as a theory of knowledge and a primitive psychology to explain how ideas get into the mind rather than simply a study of the forms of syllogism and the relationships among propositions, although he discussed these topics as well. He advocated an empirical approach to knowledge of the world, one modelled on the Epicurean canonic.

In his early Exercitationes Paradoxicae Adversus Aristoteleos, Gassendi attacked Aristotelian dialectic as overly complex and abstruse, useless as a method for making new discoveries. He used the classical sceptical arguments to question the reliability and validity of sensory experience. Since Aristotelian demonstration requires premises based on experience, Gassendi argued that the syllogisms involved cannot produce certain knowledge about the world. Moreover, since the conclusion of a syllogism contains no information not already present in the premises, syllogistic demonstration is incapable of producing new knowledge. Gassendi concluded that the entire method of Aristotelian demonstration is without foundation or utility. Not satisfied with the suspension of judgment advocated by the ancient sceptics, he opted for a middle way, ‘mitigated scepticism’. He based this approach on a series of rules or canons, which he drew from the Epicurean Canonic. These canons defined sensations, ideas, propositions and syllogisms. Gassendi then elaborated a criterion of truth, based on empiricist assumptions.

Adopting the fundamental empiricist doctrine that all ideas contained in the mind derive from the senses, Gassendi distinguished between two sorts of truth, what he called ‘truth of existence’ and ‘truth of judgment’. Truth of existence refers to the content of sensation itself. That it is what it is must be true. In this respect the senses are infallible. The sensation of gold is a sensation of gold, whether or not the object sensed is really gold or even exists. Truths of judgment, in contrast to truths of existence, are truths about the judgments we make about sensations. They are fallible, since they can assert statements about the world which might not be true. An example of such a judgment would be the proposition that this object is gold.

On the basis of this distinction, Gassendi argued that sensations, which are truths of existence that he called ‘appearances’, provide the basis for our knowledge of the world. This knowledge cannot penetrate to the inner natures of things precisely because it is knowledge of how they appear to us. On the basis of the appearances, however, it is possible to seek causal explanations, with the understanding that such reasoning is always conjectural and subject to revision in the face of further knowledge. This science of appearances can never achieve certainty, only probability, but such probability is adequate for our needs. In settling for probability rather than certainty as the epistemic goal of natural philosophy, Gassendi was rejecting the traditional Aristotelian and Scholastic conception of scientia or demonstrative knowledge. His redefinition of the goals of natural philosophy influenced the conceptions of later natural philosophers such as Robert Boyle John Locke and Isaac Newton.

4 Physics

The ‘Physics’ is by far the longest part of Gassendi’s Syntagma Philosophicum. Here he laid down the basic principles of his natural philosophy. He claimed that the fundamental components of the natural world are atoms and the void.

Gassendi began his account of the nature of things in general with a discussion of the void, since he thought that the entire universe is contained in empty space. In accordance with traditional discussions, Gassendi classified the void into three categories: the separate, extra-cosmic void; the interparticulate, interstitial, or disseminated void; and the coacervatum, produced by collecting a number of interstitial voids, usually by means of some kind of mechanical device. The question of the existence of void led him into a discussion of space and time more generally. Borrowing from the Renaissance Platonist Francesco Patrizi, Gassendi argued that space is neither substance nor accident but, rather, a kind of incorporeal extension. He thus avoided Aristotle’s error of confounding dimensionality and corporeality. Space, according to Gassendi, continues to exist even when the matter contained in it moves away or ceases to exist.

The large extramundane void is the space in which God created the universe. It is boundless, incorporeal extension. Following Epicurus, Gassendi argued that the existence of interstitial void is a necessary condition for motion; for without void spaces, there would be no place into which particles of matter could move. Other Epicurean arguments included the saturation of water with salt, the dissemination of dyes through water, the penetration of air by light, heat and cold, all of which he assumed to be corpuscular. These phenomena seemed to require empty spaces between the particles composing material bodies. Gassendi also borrowed several arguments from Hero of Alexandria (fl. 62 ad), who had drawn an analogy between the matter composing bodies and a heap of grain or sand. Just as the individual grains are separated from each other by air or water, so the particles composing bodies are separated by small void spaces. The compressibility of air, which Hero had demonstrated by means of several inventions, including the pneumatic cannon and the aeolipile (a prototype of the steam engine), seemed to call for the existence of interstitial void between the material particles composing air.

Gassendi drew on contemporary natural philosophy to argue for the existence of the coacervatum void, especially the barometric experiments of Torricelli and Pascal. Gassendi accepted the mechanical explanation of the suspension of mercury in the barometer, as the result of atmospheric pressure, thereby rejecting the Aristotelian explanation which appealed to the paradigmatic occult quality, the horror vacui. He argued that the space in the tube above the mercury is void.

Gassendi’s atoms are perfectly full, solid, hard, indivisible particles, so small that they fall below the threshold of sense. Following Lucretius, the Roman expositor of Epicureanism, Gassendi noted several commonly observed phenomena that lend support to the existence of such atoms. Wind is evidence that invisible matter can produce visible, physical effects. So is the fact that paving stones and ploughshares wear away because of constant rubbing, even though individual acts of rubbing produce no discernible change. The passage of odours through the air can be explained in terms of tiny particles travelling from the source of the odour to the nose.

Atoms possess only a few primary qualities: magnitude and figure, resistance or solidity, and heaviness. Gassendi appealed to observations using the new instrument, the microscope, to provide evidence for their small size. He also cited traditional observations such as the dispersion of pigment in water and the large quantity of smoke emanating from a smouldering log. He argued for the indivisibility of these atoms by appealing to Zeno’s paradoxes, which he interpreted as implying the absurdity of the idea of the infinite divisibility of matter (see Zeno of Elea).

Matter, in the form of atoms, is the material principle in Gassendi’s world. The efficient principle explains the causal structure of the world. The first cause is God, who created the world, including the atoms. Second causes, the natural causes operating in the physical world, are reduced to collisions among atoms moving in void space. In contrast to Epicurus who had claimed that an endless series of worlds is being produced by an eternal series of chance collisions among an infinite number of uncreated atoms, Gassendi argued that the world and its constituent atoms – a large, but finite number of them – had been created by God, who continues to rule the world providentially, with special providence for humankind. Rejecting the atomic swerves or clinamen that Epicurus had introduced to account for the collision of atoms that would otherwise only fall downward in parallel paths, Gassendi maintained that the motions of atoms had been caused by God at the beginning. Gassendi argued for God’s providential relationship to the creation on the basis of an extended argument from design.

Having established the material and efficient principles of things, Gassendi proceeded to argue that all the qualities of bodies can be explained in terms of the motions and configurations of their constituent atoms. He gave mechanical, atomistic explanations of the whole range of qualities, including rarity and density, transparency and opacity, size and shape, smoothness and roughness, heaviness and lightness, fluidity and firmness, moistness and dryness, softness and hardness, flexibility and ductility, flavour and odour, sound, light, and colour. He concluded his account of qualities with a chapter on the so-called occult qualities, in which he argued that there is no action at a distance and that even apparently occult qualities such as magnetism and the sympathies and antipathies favoured by the Renaissance naturalists can be explained in mechanical terms.

In this first section of the ‘Physics’, Gassendi created the blueprint for his version of a mechanical philosophy of nature, a Christianized version of Epicurean atomism, designed to replace Aristotle’s Physics and consonant in spirit, if not detail, with that of his contemporary Descartes (see Descartes, R. §11). In the remaining sections of the ‘Physics’, Gassendi tried to explain all the phenomena of the world in these terms. His work paralleled Aristotle’s treatises De caelo, Meteorologica, De partibus animalium, and De anima; but he took account of recent developments in natural philosophy. His intentions to mechanize notwithstanding, he wrote eclectically, often appealing to concepts and terms drawn from traditions such as Aristotelianism, Renaissance naturalism and even alchemy (see Alchemy).

Having considered the universal principles of physics, Gassendi proceeded to consider the created world, starting with celestial things. He discussed the following questions: the substance of the sky and stars; the variety, position, and magnitude of the stars; the motions of the stars; the light of the stars; comets and new stars; and the effects of the stars. In his youth, Gassendi had endorsed the new Copernican astronomy enthusiastically. The condemnation of Galileo in 1633 dampened his enthusiasm, at least in print, where he expressed sceptical doubts about being able to prove any of the three main world systems – Ptolemaic, Copernican, and Tychonic – conclusively. In the Syntagma Philosophicum, he proposed the system of Tycho Brahe as a compromise approved by the Church, but not before having stated that the Copernican theory was ‘more probable and evident’.

As for the effects of the stars, Gassendi thought astrology ‘inane and futile.’ He rejected the possibility that the stars cause terrestrial and human events. Sidereal and planetary configurations may be signs of some events on earth, such as the seasons or the weather, but they are not their causes. Moreover, the ability to prognosticate the future is the prerogative of God alone. Gassendi found horoscopes based on the moment of nativity ridiculous. Why, he asked, should the heavenly bodies have more influence at the moment of birth than at any other moment in a person’s life? He thought that the principles of astrology were based on insufficient evidence, and that astrologers often resort to deception.

Having discussed the heavens, Gassendi turned his attention to terrestrial phenomena, considering inanimate things first. He described the properties of Earth, the distribution of water and land, the tides, subterranean heat and the saltiness of the sea. He then turned to ‘meteorological’ phenomena, which included winds, rain, snow, ice, lightning and thunder, rainbows and parhelia, and the Aurora Borealis. Shifting his attention to smaller things, he wrote about stones and metals, paying particular attention to recent observations of the magnet and to the question of the transmutation of gold,which he considered possible. Finally, among inanimate things, he discussed plants which, he claimed, Epicurus had believed to be inanimate, that is, lacking soul. Gassendi discussed the varieties of plants and their parts, considering their various physiological processes, including grafting, nutrition, germination, growth, and death.

The final section of the ‘Physics’ was devoted to terrestrial living things, or animals. This section contains discussions of the varieties of animals, the parts of animals – which he described in explicitly finalistic terms, and various physiological topics including generation, nutrition, respiration and motion. Gassendi devoted about half of this lengthy section to the topics of sensation, perception and the immortality of the human soul.

Gassendi’s argument for the immortality of the soul was a key factor in his Christianization of Epicureanism. Epicurus, in order to eliminate fear of death and anxiety about punishment and reward in the afterlife as major sources of human distress, claimed that the soul is material and mortal (see Epicurianism §13). In addressing the nature of the soul, Gassendi said that the soul is what distinguishes living things from inanimate things. Adopting the distinction between anima and animus directly from Lucretius, Gassendi argued that the anima or sentient soul is material and present throughout the body but that the animus or rational soul is incorporeal. Like animals, humans possess an anima, but the possession of an animus distinguishes them from animals.

The anima was thought to be composed of very fine and intensely active atoms, ‘like the flower of matter’. It is the principle of organization and activity for the organism and the source of the animal’s vital heat. It is also responsible for perception, forming the imagination or ‘phantasy’, a physical organ which forms images derived from perception. The anima is transmitted from one generation to the next at the moment of conception.

The animus or rational soul is an incorporeal substance, created by God, infused in the body and functioning like an informing form. Gassendi argued on several traditional grounds for the incorporeality of the rational soul. We know that it is distinct from the corporeal imagination or phantasy, because we can understand some things of which we cannot form images, for example, that the sun is 160 times larger than the earth. Moreover, unlike corporeal things, the rational soul is capable of reflecting on itself. It is also able to reflect on the nature of universality per se, whereas animals, possessing only the corporeal anima, are limited to forming universal concepts without having the ability to reflect on them abstractly. Gassendi’s claim that the rational soul, in contrast with the animal soul, is incorporeal established one of the boundaries of his mechanization of the world.

Having established the immateriality of the rational soul, Gassendi proceeded to argue for its immortality. He wrote of this topic as the ‘crown of the treatise’ and the ‘last touch of universal physics’. Although he knew of the soul’s immortality on the basis of ‘the Sacred Faith’, he supported this article of faith using philosophical and physical arguments, his response to the Fifth Lateran Council’s call on philosophers in 1513 ‘to use all their powers, including natural reason, to defend the immortality of the soul’. Epistemologically similar to all reasoning in natural philosophy, the conclusions drawn from physics and philosophy could at best be highly probable. Nevertheless Gassendi was certain of the soul’s immortality which was ultimately grounded in faith.

Gassendi argued on the basis of physics that the soul is immortal because it is immaterial. Lacking matter, an immaterial thing ‘also lacks mass and parts into which it can be divided and analyzed.’ This argument was similar to arguments used by Kenelm Digby, Henry More and others. Another approach, which he called ‘moral’, argued for immortality on the grounds that the afterlife is necessary in order to compensate for various injustices in this life. Gassendi went on to argue against many detractors of the soul’s immortality, especially Epicurus against whose arguments he devoted an entire chapter of the Syntagma Philosophicum.

Gassendi’s argument that the rational soul is immaterial and immortal provides evidence that he was not a materialist, despite arguments to the contrary by some scholars, notably O.R. Bloch. Bloch (1971) bases his claim that Gassendi defended the immateriality of the rational soul only in deference to the Church on two claims: that Gassendi ascribed many aspects of cognition to the material anima; and that he did not fully articulate his arguments for an immaterial animus until 1642. Bloch’s interpretation of Gassendi as a clandestine materialist belies the fact that Gassendi’s assertion of the existence of God, angels, demons and an immaterial immortal soul is to be found throughout his Epicurean writings. These topics appear as early as a manuscript outline of his Epicurean project which he sent to Peiresc in 1631 at the inception of his project, in his letters to Valois in the 1640s, and in the posthumous Syntagma Philosophicum.

Gassendi’s Christianized Epicureanism had significant influence on natural philosophy in the latter half of the seventeenth century. Brought to England in Walter Charleton’s translation in the 1650s, Gassendi’s ideas influenced the thinking of Robert Boyle and Isaac Newton. His epistemology was also important for the thought of John Locke.

5 Ethics and political philosophy

The ‘Ethics’ comprises the third and final part of the Syntagma Philosophicum. Here, Gassendi fulfilled his youthful determination to Christianize all parts of Epicureanism. Epicurean ethics was founded on the principle that pleasure is the end of life (see Hedonism). Pleasure, according to Epicurus, consists of freedom from bodily pain and freedom from mental turmoil. The greatest pleasure is associated with the absence of both anxiety and physical pain, a state of tranquillity. The achievement of tranquillity gives individuals self-sufficiency, so that they are free to pursue their own pleasures. Epicurus recognized that not all pleasures are of equal value, and gave reason the role of calculating pleasure and pain. In this way, he could claim that long-term pleasure was of greater value than short-term pleasure that might lead to long-term pain. The freedom humans need to implement the calculus of pleasure and pain was insured by the random swerve of atoms, the clinamen, which added a dimension of indeterminism to the human soul which Epicurus believed to be composed of atoms. Epicurean hedonism did not receive a good press, either in antiquity or in the Christian Middle Ages. Dogged by Epicurus’ reputation for atheism and moral decadence, this philosophy needed to be restored and Christianized in order to be acceptable to orthodox intellectuals in the seventeenth century. Gassendi addressed this task in the ‘Ethics’.

Although Gassendi accepted the Epicurean principle that equated pleasure with the good, he reinterpreted the concepts of pleasure and human action, thereby creating a Christian hedonism which found a natural place in his providential worldview. Gassendi described four kinds of pleasure: the instinctive desire for pleasure that even irrational creatures possess; the calculated strategy of maximizing physical pleasure; the prudence of the wise who understand that true pleasure consists of tranquillity and the absence of pain; and finally the sublime pleasure of the beatific vision of God. The prudence of the wise is based on understanding the vanity of most human desires. The wise person will employ the calculus of pleasure and pain to achieve the state of tranquillity. Gassendi united this hedonistic ethics with his providential worldview by claiming that God has instilled in humans a natural desire for pleasure and a natural aversion to pain. In this way, God guides human choices, without negating free will. The prudent pursuit of pleasure will ultimately lead to the greatest pleasure of all, presence with God in heaven.

Consistent with the voluntarist theology that informed all of Gassendi’s philosophy, the ‘Ethics’ presumed both divine and human freedom. Human freedom is a necessary concomitant of voluntarism, for if human actions are inexorably determined, that determinism will limit God’s freedom to intervene in their lives. Gassendi considered true freedom, libertas, to be the freedom of indifference, the ability of the mind to make judgments and take action without being determined in one direction or another. This kind of freedom gives reason a central role in moral deliberation. Gassendi contrasted libertas with libentia – spontaneity or willingness – which is characteristic of boys, brutes and stones, creatures that are impelled to move in certain ways, but not on the basis of judgments deriving from the freedom of indifference.

Gassendi’s emphasis on freedom, both human and divine, led him to consider the question of predestination, which was the main context for discussions of freedom and determinism in the post-Reformation setting. How can human action be free if God has foreknowledge of who will be saved and who will be damned? Influenced by the Jesuit Luis de Molina’s moderate stance on the question of predestination (see Molina, L. de; Predestination), Gassendi argued that God created people free to choose, even though he knows from his eternal viewpoint how they will choose. Gassendi, following Molina, claimed that divine foreknowledge does not interfere with human freedom. Similar concerns with free will led Gassendi to reject both Stoic fatalism and astrology.

Gassendi’s hedonism led him to formulate a political philosophy based on the idea of pactum or contract (see Contractarianism). Starting from the idea of a hypothetical state of nature in which there was no secure ownership of property, a state which would inevitably degenerate into turmoil and conflict, Gassendi argued that individuals could secure greater happiness for themselves by forming societies. These societies are based on pacts or contracts in which both individual rights and property rights are defined and in which the weaker are protected from the stronger. The contracts establish rights, which Gassendi considered natural in the sense that they follow from the calculus of pleasure and pain. Civil society is thus a natural outcome of human nature. A system of justice comes into being to restore rights that have been violated and to prevent further violations. Gassendi favoured monarchy as simpler and more efficient than the other traditional forms of government. However, he argued that the power of the monarch remains answerable to the consent of the governed who first established the contract. He was therefore opposed to absolutism on the grounds that the absolute monarch had severed his relationship with the governed and was consequently answerable to no one. Gassendi developed his political philosophy in close contact with Thomas Hobbes, and his ideas had a profound influence on John Locke, who is usually named as the founder of the liberal tradition in political philosophy (see Liberalism).