In the West, 17th-century philosophy is usually taken to start with the work of René Descartes, who set much of the agenda as well as much of the methodology for those who came after him. The period is typified in Europe by the great system-builders — philosophers who present unified systems of epistemology, metaphysics, logic, and ethics, and often politics and the physical sciences too. Immanuel Kant classified his predecessors into two schools: the rationalists and the empiricists, and Early Modern Philosophy (as 17th- and 18th-century philosophy is known) is sometimes characterized in terms of a supposed conflict between these schools. The three main rationalists are normally taken to have been René Descartes, Baruch Spinoza, and Gottfried Leibniz. Building upon their English predecessor Francis Bacon, the two main empiricists of the 17th-century were Thomas Hobbes and John Locke. The former were distinguished by the belief that, in principle (though not in practice), all knowledge can be gained by the power of our reason alone; the latter rejected this, believing that all knowledge has to come through the senses, from experience. Thus the rationalists took mathematics as their model for knowledge, and the empiricists took the physical sciences. This emphasis on epistemology is at the root of Kant's distinction; looking at the various philosophers in terms of their metaphysical, moral, or linguistic theories, they divide up very differently. Even sticking to epistemology, though, the distinction is shaky: for example, most of the rationalists accepted that in practice we had to rely on the sciences for knowledge of the external world, and many of them were involved in scientific research; the empiricists, on the other hand, generally accepted that a priori knowledge was possible in the fields of mathematics and logic.
This period also saw the birth of some of the classics of political thought, especially Thomas Hobbes' Leviathan, and John Locke's Two Treatises of Government.