Monism vs Dualism

Rene Descartes certainly didn't lack for credentials. As the "Father of Rationalism," "Father of Modern Philosophy," and originator of Cartesian geometry, he had more than enough interests to fill his spare time. But his role as "Father of Skepticism" helped popularize a major change in thinking about the nature of human experience. Dualism, or the doctrine that mind and body are of two distinct natures, is one of the key philosophical problems inherited by psychology. In both philosophy and psychology there have been several attempts to reconcile the mind and body.

On the dualism side of the argument, psychophysical parallelism and psychophysical interactionism have been advanced as explanations for the workings of mind and body. Parallelism has it that mental and physical events are independent of one another but occur simultaneously. Philosophers such as Leibnitz, for example, held that the activities of the mind and body were predetermined, and that both simply ran their course in a carefully orchestrated, synchronized, yet independent fashion. Interactionists, on the other hand, hold that mental and physical events are related in a causal way, such that the mind can influence the body and vice-versa. Descartes championed this idea with his notion that humans are "pilots in a ship;" mental beings who guide physical bodies through the world. Both psychophysical parallelism and psychophysical interactionism agree that the mind and body are of two different natures, and disagree over how closely those natures may interact.

Monists, by comparison, argue that there is one nature to things, although they disagree about whether it is primarily mental or primarily physical. Subjective idealism (or "mentalism," as it is often called), argues that there is only the mental world, and that the reality of the physical world is suspect. George Berkeley, for example, provided numerous arguments as to why the essence of existence is to be perceived; when not in direct perception the physical world cannot support the claim of its existence. (Berkeley, by the way, apparently hated walks in the forest, for fear of all those falling trees that he may or may not have heard.) In contrast, materialistic monism takes the position that there is only physical "stuff" to the world, such that ideas, thoughts, and images are actually physical events in the body. Many modern biological scientists would agree with this form of monism, arguing that the brain is primary while the "mind" is either illusory or epiphenomenal.