René Descartes’s concept of the self revolves around the idea of mind-body dualism. For Descartes, a human person is composed of two parts, namely, a material body and a non-material mind.
It must be noted that Descartes’s idea of the “mind” is not different from the idea of the “soul” understood in antiquity, for instance, Plato’s concept of the soul.
For Descartes, the mind, or the soul, is superior to the body for it is in the mind that “mental states” occur. This is because for Descartes, the mental states, such as thinking, imagining, and analyzing, rather than the physical states of the body, such as pain, hunger, and thirst, are fundamental to our life as persons. In other words, for Descartes, it is the mind that makes us humans. Thus, for Descartes, the “mind” is the “real self”.
But how does Descartes view the soul as the true self of humans and how does it differ from the body?
On the one hand, Descartes’s understanding of the body as a material entity consists in extension (res extenza). In fact, according to Descartes, all things in the material world can be understood and explained in terms of size, shape, and motion. Hence, to be a “body” for Descartes is
1) to have size and shape,
2) to endure, and
3) to be movable and changeable.
The main reason why Descartes puts premium on “extension” as the essence of bodies or material things is that the conception of the things’ extension, such as size or shape, is clear and distinct. In other words, one cannot doubt the size and shape of a thing. For example, if one is holding a pen, one cannot doubt that it is tubelike and a bit small. But if we talk about the other purported features of a thing, such as color and taste, Descartes says that they are obscure and confused. Hence, these attributes do not constitute a thing. For example, the color red is not what makes a rose truly a rose. A rose flower can be white or yellow. It doesn’t have to be red for it to be called a rose. Later on, Jonh Locke calls these qualities “secondary qualities”, which for him do not necessarily constitute a thing.
On the other hand, as explained in his second meditation, Descartes argues that the mind or soul is an immaterial, nonextended substance that thinks (res cogitans). By “thinking” Descartes means being conscious of one’s self and the object of its thinking. Thus, for Descartes, the mind as the true self of humans is a thinking thing. And it is interesting to note that, according to Descartes, knowledge of oneself as a subject of conscious states and acts is the most certain knowledge anyone can have.
But how does Descartes view a thinking thing?
For Descartes, a thinking thing is a being that doubts, understands, asserts, denies, wills, imagines, and the like.
In Meditation II of his seminal work titled Meditations on First Philosophy, Descartes demonstrates how certainty can be attained.
As already mentioned, Descartes is convinced that he can be certain that he exists because if he doubts, there must be a thinking mind that does the doubting. Thus, Descartes famously say: “I think, therefore, I am”. According to Descartes, this statement is indubitable because even if a powerful demon were to deceive him into thinking that he does not exist, he needs to exist in order for the demon to deceive him. Therefore, whenever Descartes thinks, he exists.
From here, Descartes proceeds to addressing the question “What is this ‘I’ that does the thinking?”.
Descartes, however, concedes that though what he perceives with his senses may be false, he cannot deny that he is perceiving. Thus, for Descartes, the human mind is capable of both thought and perception. In other words, for Descartes, sensation or perception belongs to the mind. As a matter of fact, sensation is one of the functions of the mind (the other is thinking). Descartes uses the analogy of the wax to prove his point.
As we can see, a solid wax and melted wax are the same wax. For some thinkers, such as the empiricists, it is the senses that distinguishes a solid wax from a melted wax. For Descartes, however, the ability to distinguish a solid wax from a melted wax is not the function of the senses but of thought. In other words, it is “thought” or the “reasoning mind” that makes the judgment that a solid wax and melted wax are the same wax.
For Descartes, therefore, because the senses can be deceived, physical objects, including bodies, are properly perceived only by the intellect. Indeed, for Descartes, the mind is the only thing that one can be certain of.
Finally, Descartes believes that the mind and body are both substances (please note that in traditional metaphysics, the term substance refers to anything that can exist on its own independent of anything else). Therefore, for Descartes, mind and body are completely distinct and that they are independent from each other.
Although they are completely distinct from each other, Descartes argues that the mind and body are in some sense unified. For Descartes, this union is what makes possible the interaction between mind and body.
So, despite the real distinction between mind and body, Descartes argues that these substances nevertheless interact with each other. According to Descartes, the mind causes certain changes in the body and the body in the mind.
Part of the reason why Descartes aims to establish the distinction between mind and body is to establish the fact that the soul is immortal. As we can see, the distinction between mind and body opens up the possibility of establishing the immortality of the soul since it involves the idea that the “decay of the body does not imply the destruction of the soul”.
But how does Descartes prove the crucial claim that the mind and body are capable of existing apart from each other?
Here, Descartes invokes what he calls 1) clear and distinct conception of the mind as a thing that is complete and does not require any extended qualities in order to exist, and 2) the corresponding clear and distinct conception of the body not requiring any mental properties in order to exist.
As we can see, Descartes’s real distinction argument turns on the reliability of so-called clear and distinct perception. However, Descartes did not give a concrete example of a mind existing apart from the body, and a body existing apart from the mind.
Also, when asked about the specificity of this interaction, Descartes was unable to answer and instead appeal to God. In Descartes’ understanding, God sets up or institutes those particular causal relations between mind and body that are, in general, the most conducive to the well-being of the composite of mind and body.