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.
Mixture and Transformation in Aristotle’s De generatione et corruptione