§51. A New Epicurus

Pierre Gassendi was a scholar and humanist, but he was more, something that such people usually were not—in a modern biographer’s words, he was a “tireless student of nature, whose time is spent no less in the observatory and the laboratory than in the library, whose correspondence is filled with new information exchanged, fresh discoveries analyzed, observations recorded and compared.” Another scholar observes that among the savants of the early seventeenth century, “only Gassendi, whose awareness of empiricism’s roots and implications is evident across his intellectual pursuits, integrates philos­ophy and science on what he believes to be strictly empiricist grounds.”¹

Gassendi was an empiricist because he was an Epicurean.

Empiricisms. Barry Allen, Oxford University Press (2021). © Oxford University Press.

DOI: 10.1093/oso/9780197508930.001.0001. also Intellection and ratiocination, and therefore all human Souls, to arise from the mere Contexture of corporeal Atoms, and utterly explode all incor­poreal Substances.” In his notebook Berkeley epitomized the degeneracy still associated with Epicurus: “Fall of Adam, rise of Idolatry, rise of Epicurism and Hobbism.”²

Gassendi got the idea of doing for Epicurus what Thomas Aquinas did for Aristotle.

Before he was an Epicurean, Gassendi was an anti-Aristotelian. His early Paradoxical Exercises Against Aristotle (1624) attacks the whole system of scholastic education (he was then a professor at Aix), with acerbic gibes that echo Bacon. “When they enter their schools they enter into another nature which has nothing in common with this nature outside.” Aristotle’s logic “does not open up nature, but only acts like the man who promises the dis­covery of a treasure saying, ‘Search where it is hidden and you will find it.’ ” The Peripatetic system has corrupted philosophy with petulant disputes, barbarous language, undue reverence for the founder, ignorance of other authors, and indifference to observation and experience. By 1624, however, learned explosions of Aristotle were a genre, and Gassendi had nothing new to say. He wisely decided it was impossible to dislodge Aristotle by mere crit­icism. Nothing avails short of an alternative natural philosophy. Already having a scholarly interest in the philosophy of The Garden, he championed a rehabilitated Epicurean natural philosophy.³

Gassendi’s atomism begins with Epicurus but goes beyond him (and Lucretius) in several respects. He follows Epicurus in allowing incorporeal void, but adds an incorporeal soul and an incorporeal divinity, while with­drawing from Epicurus’s contention that the quantity of atoms is infinite, be­cause God alone is infinite. Gassendi obviously rejects the idea that atoms are eternal and uncreated. God created the atoms, and there is no absurd swerve, their motion arising not from brute collision but rather from a tendency God put into the atom at the beginning.

Gassendi’s work, all in Latin, was widely read in his lifetime, and continued to find an enlightened audience in the eighteenth century. Voltaire, Holbach, and Diderot all read Gassendi’s Opera, and many others knew his ideas from Francois Bernier’s French abridgement, which was one of the most widely read books of the latter seventeenth century. Thomas Jefferson, an ardent Epicurean, admired Gassendi over Lucretius. Physicians gathered around Gassendi, Bernier first of all, a Montpellier medical graduate who attended Gassendi as physician in his last years and at his death, also befriending Locke (another physician) during the latter’s French sojourn. Gassendi found an audience among English physicians too. Walter Charleton, his most prominent English follower and among the first elected members of the Royal Society, was physician to Charles I.⁴

Gassendi’s empiricism is not antiquarian, or not entirely so. The way he tilted and readjusted ancient empiricism, what he chose to emphasize, and what he discreetly or ostentatiously discarded became a profile of empiricism in natural philosophy for the next century. He maintains, against Aristotle no less than Descartes, and against the ancient Skeptics and their Renaissance revivalists, that the evidence of the senses is trustworthy and warrants prob­able credibility. Knowledge begins with experience, and a priori knowledge or innate ideas are impossible. Natural philosophy should dispense with syl­logistic certainty and pursue observation and measurement. Beliefs about nature have to be revisable, even so-called truths of reason depending on the senses. “The whole is greater than the part” is known by enumeration, and all triangles have three sides is an induction.

Epicurus built his empiricism on Aristotle, ingeniously recreated with atoms. Aristotle explained aisthesis (perception) as “a kind of being moved upon and acted upon.” Like Plato, he emphasized passivity; aisthesis is a pas­sion to which the body is driven by an involuntary impress. For Aristotle, as for Epicurus and Gassendi, what we perceive are not essences but quali­ties, and each sense is unerring in its special object. For Plato, passivity is a reason to disqualify perception as knowledge, a decision Aristotle suspends. Following Democritus, he makes passivity key to perception’s scientific con­tribution, an argument Epicurus and Gassendi reiterate. “[Since] deception, or falsity, is not to be found in the senses themselves, which merely behave passively and only report things as they appear and must appear given their causes, it is to be found in the judgment, or mind, when it does not act with enough circumspection.” Aristotle recognized in experience an organ for the development of science, an instrumental role Epicurus amplified although dispensing with syllogistic. Practically all human knowledge rests on reliable sensory cognition that is independent of reasoning, mechanically induced by the operation of sense.⁶

There is more to Gassendi than Epicurus rehabilitated. He is also a fol­lower of Carneades and Hellenistic probabilism. Gassendi demands for him­self “the liberty to live from day to day, and not to advance or entertain what goes beyond the limits of pure probability (probalilitatis)” The insight he takes from Carneades is that we know only the shell or surface of things and cannot examine or otherwise know their inner nature.

To Pyrrhonist skeptics, scientific knowledge seems impossible. The appearances that we know are not the proper object of science, which is sup­posed to be about nature, not about us or our affections. Gassendi turns the argument on its head. Because sense appearances are the beginning and end of natural knowledge, it should be possible to make a science from them. We need but discard Aristotle’s discredited canon and give the noble word scientia a use closer to our real powers, a scientia with an entirely phenom­enal base, an empirical scientia. The conclusion of Gassendi’s early diatribe against Aristotelianism was entitled, “That There Is No Scientia, Especially Scientia as the Aristotelians Describe It.” That was before he immersed him­self in Epicurus and probabilism. Epicurus sustained his belief in the value of science, which he takes from the hands of the Aristotelians and makes more consistently empirical.⁸

Ancient skeptics were more interested in tranquility than knowledge, while Gassendi seeks a new concept of science. Something survives the skep­tical assault on classical knowledge, namely, the phenomena. This fragment, amplified by a logic of signs, is the point of departure for a new sort of science. In place of apodictic demonstration, let us have the probable, the analog­ical, the likeness of truth, experimentally verified. Probability is embraced, certainty repudiated, discovery and advancement extolled and expected.

Reference to hunting reactivates the venatic image of hunting out nature’s secrets, which Galileo and Bacon also found seductive (§37). To chase down obscure clues is a pursuit of signs, perceptible indications of unseen causes, and the ancient medical locus for the argument about the value of reason and theory in medicine. Epicurus, probably following Democritus, took the medical sign into natural philosophy, praising one who “follows rightly the appearances and takes them as signs of what is unobservable.” Ancient medicine’s theory of signs is the centerpiece of Gassendi’s argument for an empirical reorientation in natural philosophy. He follows Sextus (who was following Stoics and the doctors) in distinguishing commemorative (hupomnestikon) and indicative (endeixis) signs. Commemorative signs are remembered associations, and even Skeptics allow them. Indicative signs supposedly indicate things naturally non-evident, the unseen causes of per­ceived events; for example, that a red face is a sign of disease, because a red face is caused by excess heat and excess heat is a cause of disease.¹⁰

Whereas skeptics like Sextus reject indicative signs because they depend on the hypothetical causes that empiricists denounce as non-evident, hence uncertain, and unethical in medicine, Gassendi rehabilitates them, as Galen had in antiquity. Gassendi’s favorite example is sweat as an indicative sign of invisible pores. Moisture is corporeal; nothing corporeal can pass through an obstruction except by a passage; the obstruction is the skin; so passages, pores, must exist in the skin despite their invisibility. The inference was Hippocratic, but remained a mere hypothesis until confirmed by the mi­croscope in Gassendi’s time. Democritus explained the appearance of the Milky Way as an indication of innumerably many stars whose light became a blur from a great distance, again confirmed in Gassendi’s time by telescopic observations. Gassendi takes these eventually confirmed inferences as evi­dence that the mind can understand things about bodies on its own, which may only later (or never) be perceived. How could an atomist think other­wise? Atoms assuredly will never be perceived.

Sensation gives only a sign, which the judging mind can accept or reject. This mind must be controlled by sense, taking initiative solely from the sen­sible given, as Gassendi argued against the Rosicrucian fantasies of Robert Fludd. Yet sense too must be controlled by reason. “Unless the human mind is governed by experience and observation, it is utterly sterile, fruitless, and extremely fertile in nonsense.” The argument may sound familiar. Galen abolished the ancient dichotomy between reason and experience; the only experience that counts, or from which we learn, is a qualified, disciplined, hypothetical experience. “The art of healing was originally invented and dis­covered by the logos in conjunction with experience. And today also it can only be practiced excellently and done well by one who employs both of these methods.”¹¹

Gassendi enjoyed a European readership and was avidly studied in Britain. One scholar thinks “it would be difficult to imagine a more receptive climate for Gassendi’s influence than England in the late seventeenth century,” due to the appeal of probabilistic reasoning and modesty in claims to know­ledge, and interest in mechanical ideas of nature. Gassendi was involved in barometric experiments from an early point, publishing the first detailed description of Torricelli’s experiments and the first account of Pascal’s bar­ometric experiment at Puy-de-Dome, so it is no surprise that Boyle was an enthusiastic reader of the French pere, “a great favorite of mine,” whom he credits with the modern formulation of the corpuscular hypothesis. He follows Gassendi on many points, sometimes through the intermediary of Charleton’s Physiologia Epicuro-Gassendo-Charletoniana (1654), the first work in English to present Epicurean atomism as a mechanical philosophy, which Boyle enthusiastically recommended to Newton.¹²

Contemporaries associated Locke and Gassendi, at least Leibniz did. “This author [Locke] is pretty much in agreement with M. Gassendi’s system, which is fundamentally that of Democritus... and he seems to agree with most of M. Gassendi’s objections against M. Descartes.” Formerly, scholars dismissed the association; now the chorus bends the other way, describing Locke as a Gassendist, even Gassendi’s most important follower. Gassendi can certainly sound as Locke will sound (and resound) throughout the eight­eenth century; for instance, explaining how every idea derives from sense, he adds, “It is this, then, that the celebrated saying, There is nothing in the intellect which is not first in sense, means. This is also what is meant by the claim that the intellect, or mind, is a tabula rasa, on which nothing has been engraved or depicted.”¹³

For Gassendi, as for Locke, experience is the only source of knowledge, and for Locke, as for Gassendi, we have no innate ideas. The resemblance in their doctrine is unlikely to be accidental, and it is clear that Locke had thorough knowledge of Gassendi’s works. References begin to appear in his notebooks from the time he met Boyle, including quotations from sev­eral of Gassendi’s works, and transcriptions of passages from Boyle praising Gassendi. While in France Locke met the leading Gassendists, including Bernier, whose abridgement of Gassendi he carried home with him. Scholars find virtually Locke’s entire theory of ideas in Gassendi’s Institutio logica, and seem right to conclude that Gassendi’s theory is Locke’s starting point for the Essay.¹⁴

Ironically, one place where Locke refused to follow Gassendi is also where Locke will be criticized by later French empiricists, especially Condillac. While Locke allowed reflection as a second source of experience, Gassendi is a stricter sensualist, maintaining the more consistent empiricism that Condillac urges as a correction to Locke. “Every idea either comes through the senses, or is formed from those which come through the senses,” Gassendi writes. The source of ideas is in every case the world beyond, with nothing corresponding to Locke’s “reflection.” To Condillac, Locke’s departure from Gassendi’s more consistent empiricism was his biggest mistake.¹⁵