Descartes Substance Dualism

According to Descartes, our minds and our bodies are two distinct substances capable of existing apart, which is called substance dualism. A substance is a particular kind of matter with uniform properties, meaning that something is a substance if it needs no other thing in order to exist. His argument is rooted in the idea that the essence of the mind is thought, and the essence of the body is extension. Descartes defines extension through his understanding of matter, which he believes has spatial extension, and is what takes on true form and essence. He argues that if a person can clearly and distinctly perceive something, then God makes that something that exists correspond to the person’s clear perception. This idea is depends on the consistency

If these two things can in fact exist apart then they are truly distinct. Descartes drew from this that a person can clearly and distinctly perceive the mind as a complete thing to which extension does not pertain, and also that the body can be clearly and distinctly perceived as a complete thing which thought does not pertain. Descartes then concludes that the mind and body exist apart from each other and therefore they are really distinct from one another.

Descartes’ account of substance dualism brings up some problems. One objection is the idea of causal interaction between the mind and body. If the mind and body are clearly and distinctly perceived as separate from the other, then persons cannot causally influence bodies. However, we know that persons can causally influence bodies, and therefore, substance dualism is false. For example, the mind is not in control of the body the way that a pilot is in control of a plane. The union between the mind and the body is complex because minds are immaterial and non physical, while the body is physical and material. This leads to the next question which is: how can the mind and body causally interact if the mind and body are truly distinct substances? Descartes claims

The mind and body, if still only connected by the penial gland, are not completely distinct if connected in this way. The consequences of this problem are very serious for Descartes, because it undermines his claim to have a clear and distinct understanding of the mind without the body. For humans to have sensations and voluntarily move some of their bodily limbs requires a surface and contact. Since the mind must have a surface and a capacity for motion, the mind must also be extended and, therefore, mind and body are not completely separate. This means the “clear and distinct” ideas of mind and body, as mutually exclusive natures, must be false in order for mind-body causal interaction to occur. Hence, Descartes has not adequately established that mind and body are two really distinct substances. The mind is not fully independent of the body, nor is the body completely independent of the mind, and therefore both cannot be understand as separate substances according to Descartes definition. The body as an extension cannot function without the mind, and the mind cannot exist as separate from the body. Therefore the dualistic nature that Descartes suggests is