Perception and Thought Leibniz’s Criticism of Descartes’s Denial of Perception to Animals

Cartesians equate all mental acts, such as sense-perceptions, affects, and desires, with conscious thought. This equation, Leibniz argues, leads Cartesians into a dilemma: either animals perceive, but then they also think; or they do not think, but they do not perceive either. To argue against the Cartesians that animals do perceive but do not think, Leibniz rejects the equation between perception and thought. In developing the distinction between perception and thought, I argue that Leibniz endorses the thesis that heightened and distinguished sense-perceptions are not the highest common factor between humans and animals. This perspective sheds new light on a much debated question in Leibniz scholarship: What is the relationship between consciousness, reflection, and apperception according to Leibniz’s theory of human and animal cognition?