Dualism: Mind, Body, and the Rejection by Science

What Is Dualism?

Dualism is the metaphysical principle that there are two substances — that is, distinctive and autonomous kinds of being — one material and the other spiritual. Material substance is defined as physical and is considered to be the fundamental certainty of the empirical world: the world we see, hear, and measure with our senses and with technical instruments that extend the range of the senses, such as electron microscopes, telescopes, and radar. The spiritual world is usually described negatively as a non-physical, non-material reality underlying the non-empirical world, variously called the psychological, the mental, or the spiritual world.

The principle of dualism predates the scientific study of behavior. The assumption that "the person" comprises two systems — mental and physical — provides epistemic justification for asserting that behavioral measures count as evidence of other systems. Throughout the psychological literature, behavior is treated as apparent scientific evidence of the presence, action, or malfunction of systems, processes, or events internal to the person (Selk, 2001, p. 871).

In dualism, "mind" is contrasted with "body," but at different times, different aspects of the mind have been the center of attention. In the classical and medieval periods, it was the intellect that was thought to be most obviously resistant to a materialistic account. From Descartes onward, the main stumbling block to materialist monism was supposed to be "consciousness," of which phenomenal consciousness or sensation came to be considered the paradigm instance. Dualism resolved a conflict for Descartes between his materialist interests and important religious concerns of his time by allowing him to distinguish mechanical behavior from behavior generated by something called "free will." The assumption of two domains continues to underpin scientific accounts of human action.

Descartes and the Origins of Mind-Body Dualism

Descartes was a scientist who not only wanted to contribute to empirical knowledge but also felt the constraints imposed by the Roman Catholic Church. He yearned for the kind of freedom to pursue scientific endeavors that Galileo had not found, and so he proposed a solution to this practical difficulty. He felt pulled in two directions: on one hand, he was a committed Catholic; on the other, he was a committed scientist. The two endeavors seemed to be in conflict.

The solution lay in separating these two commitments into different realms, and that is precisely what Descartes suggested. The dualism of mind and matter held that there were two radically different kinds of reality, each sufficient in itself and each requiring a different methodology with different assumptions. Descartes relied on the alleged indivisibility of mind and on a conception of the physical as divisible — a conception that rested on his conviction that the essential properties of physical reality are all geometrical properties.

Arguments for Dualism and Belief in Immortality

Dualists are often drawn to a belief in immortality. If there is another type of reality besides the body, this non-body can survive death. The non-body can conceivably exist eternally in a non-physical world, experiencing non-physical pleasures or pains distributed by a non-physical God. This notion may seem difficult to defend rigorously, but it apparently gives many people great comfort and hope.

Some dualists draw a significant inference from the fact that we use different kinds of language to talk about physical things and non-physical things. They note that when we talk about physical things, we use language that locates or causally connects objects in space. When we talk about processes such as thinking, however, we do not use the language of things in space. We do not think of thinking as taking place in a particular location or of a thought as having physical dimensions.

From this observation about language, dualists infer that the non-physical is a substance — that is, a type of reality capable of independent existence, not reducible to some other phenomenon. Most dualists would agree that colors, for example, are not substances because colors do not have independent existence: they are reducible to other phenomena such as light and sensory apparatus. Yet many dualists would deny that thinking, perceiving, willing, and desiring are reducible to material processes (such as brain states). They believe these psychological or mental activities are best explained as functions of a non-physical substance. Such activities can certainly be coherently explained by dualism, but it is not necessary to invoke the belief in non-physical reality to explain everything that is difficult to describe physically (Author not available, The Columbia Encyclopedia, 2002).