In the seventeenth century, European thought about the capacities of a perfectly rational mind (i.e. that of the best pagan philosopher) underwent a major transformation. This transformation had three sources: (i) philological scholarship concerning the history of religion that rejected patristic narratives of pagan/Judaeo-Christian similarity; (ii) reconsiderations of Asian theology as reported by missionaries and travellers; (iii) new approaches to pagan philosophy, which was more and more conceived of as fundamentally incapable of achieving the ‘true’ metaphysical and cosmological worldview held by Christians, above all because of its universal adherence to the rational principle of ex nihilo nihil fit. As a result, by 1700 a consensus emerged that the rational pagan mind bereft of revelation would tend to some kind of animism, pantheism, vitalism, or even monism. The debate was whether this pagan worldview concealed a latent monotheism (a view held by John Selden, G.J. Vossius, Tobias Pfanner, Ralph Cudworth, and others) or to a monistic atheism (a position first articulated by Pierre Gassendi, and then further developed by Jakob Thomasius, Samuel Parker, François Bernier, and many others). By the end of the century, the second view had largely triumphed.

The Scientific Revolution completely transfigured the European intellectual landscape. Old divisions disappeared, while new fault lines emerged. Ancient philosophical sects had been replaced by new schools, featuring novel masters, disciples, and methodological commitments. However, the new schools still engaged in antagonistic discourse, attacking one another along new fronts—e.g., Cartesians against Gassendists, Newtonians against Leibnizians. This chapter presents the diverse philosophical camps that arose in the later stages of the Scientific Revolution by noting a shift in the use of the term ‘sect’. While it still signified something like an Ancient philosophical school for some, it could also take on a more negative polemical meaning, intended to disparage one’s opponents. Moreover, the individuals associated with the “sects” did not all faithfully subscribe to explicit, coherent, and systematic programs. On the contrary, declaring membership of a sect was as often a signal of opposition as of allegiance to a methodology or theory. Despite calls for conciliatory research programs, sectarian attitudes did not disappear by 1750, but delineated new battle lines between the Cartesians, the Leibnizians, and the Newtonians.

In the Scientific Revolution the concept of body evolved along several divergent lines, from conceptions that rely exclusively on extension and motion to more elaborate accounts that include attributes such as solidity and force. A host of complications were disputed, such as atomism versus the infinite divisibility of bodies, the distinction between primary and secondary properties, and the possibility of a vacuum. This chapter explores these and other issues, but with an emphasis on the relationship between body and spatial extension. Descartes's three-part distinction—i.e., whether the relationship between body and extension is conceptually, modally, or really distinct—serves as a framework for investigating the development of early modern theories of material body, a process that laid the basis for the ontology and epistemology of modern science.