Abstract

The philosophers René Descartes (1596–1650), Nicolas Malebranche (1638–1715), Benedict Spinoza (1632–77), and Gottfried Wilhelm Leibniz (1646–1716) are grouped together as rationalists because they held that human beings possess a faculty of reason that produces knowledge independently of the senses. In this regard, they contrast with empiricist philosophers, such as John Locke and David Hume, who believed that all knowledge arises from the senses. The rationalists contended that proper use of reason would yield the first principles of metaphysics, the most basic science of all. Metaphysics was also called “first philosophy,” and it took as its subject matter nothing less than the basic properties and principles of everything. For our purposes, it is important to note that the rationalists believed that metaphysics could provide foundations for specialized disciplines, including ethics and physics, and also medicine and other applied subjects. The rationalists and their followers developed theoretical positions of ambitious intellectual scope, ranging from metaphysical conclusions about the existence and nature of God to detailed theories of physical and physiological processes. Although they put great store in the faculty of reason for establishing overarching principles, they looked to observation and experience to provide data and evidence for their detailed theories. They took special interest in the metaphysics and physics of the human organism, and this led them to psychological topics concerning the characteristics and principles of animal behavior, the process of sense perception, the passions, and emotions, and appetites, the cognitive operations of the mind (including attention and understanding), and the relation between mental phenomena and bodily processes in the brain and sense organs. The various rationalists, but especially Descartes, made original contributions to these topics. After considering the character of psychology as a discipline in the seventeenth century, we will examine these contributions in turn.