Oh Philosophy of Mind is such a piece of cake. We got back our midterms today, which were three take-home essays! Scores: 95, 93, 93. 
The first question:
1. Explain Descartes’s Evil Genius Conceivability Argument for Dualism. Be sure to explain all relevant technical notions (essential property; Leibniz’s Law), and be sure to make a case for the truth of the argument’s premises. Finally, give an objection to the argument.
My 95/100 response:
Rene Descartes, a famous philosopher and mathematician of the 17th century, authored the famous words, “I think, therefore I am.” In “Meditations of First Philosophy” Descartes goes on to explain and argue for his viewpoint, now called Cartesian Dualism. Descartes asks, in essence, what he is. He believes himself to be a mental substance: a mind or a subject of mental states. Mental substances are then not physical. The body is a physical entity, but in referring to oneself and even in pointing to the body that is not the core of what one is, according to Descartes. Mental states are not physical states; a physical state can be the solidity of water formed into ice.
In order to prove Cartesian Dualism he first ignores all his opinions and releases himself of judgment; he conducts a conceivability argument called The Evil Genius Conceivability Argument. He establishes that he in fact exists, but introduces the notion that an evil demonic creature has set out to deceive him and creates an alternate possible reality. “[T]he sky, the air, the earth, colours, shapes, sounds, and all external things” are nonexistent and mere figments of the imagination. In this thought-world nothing physical exists, not even the body, but Descartes believes to have a body because of the deception of the Evil Genius. However, he is exactly the same as he is in actuality: all his beliefs, experiences, desires, and thoughts, but they too are caused by the ‘Evil Genius’. Using the Evil Genius Thought Experiment, Descartes forms the basis to his conceivability argument.
The argument’s first premise says that he does not have the property of being essentially extended, which must be distinguished as being different from being extended, the emphasis on ‘essentially’. It is not saying that a person lacks extension. This premise originates from the thought experiment, and is a logical possibility. The second states that the body has the property of being essentially extended. This premise is true based on the obvious fact that the body indeed takes up space as any and every physical thing does, making it true that all physical things are necessarily extended. The resulting conclusion from the conceivability argument is that the “I” is not “the body” using Leibniz’s Law.
So to explain this argument the words within it need to be explained. Since the emphasis in the first premise is on the word “essential” what then does it mean? Item A has property B, and property B is an essential property of A by definition meaning that it is logically impossible for item A to exist and lack B for B is the defining property that makes A, well, A. Again, to be extended simply means occupying a portion of physical space. For the body to be essentially extended means that by definition it is a physical thing that occupies space, a logical and obvious fact. By the Evil Genius Thought Experiment it is logically possible for the mind to exist without a body (though under deception of being with a body) and still exist. This makes premise one logical. Using the two premises he concludes with Leibniz’s Law, a widely used proven truth, that if C is identical to D then C and D share all the same properties. Since the mind and body do not share the property of being essentially extended they cannot be one and the same. The conclusion is dualistic in nature because the mind is a non-physical (or rather, mental) substance.
The argument is valid, meaning the logic makes sense and both premises are plausible or conceivable but not necessarily true. So, are the premises true? A valid argument with all true premises is a sound argument, but the truthfulness of the premises can be debated. Conceivability arguments are in fact, not guaranteed to be logical. It is possible that the Evil Genius Conceivability Argument has hidden within it a logical impossibility (in which a contradiction arises). The Lost Bet Thought Experiment proves this point: imagine a world in which you have lost a bet and as a result must accomplish certain tasks as repayment. This is conceivable, so everything is okay… so far. The tasks can include any number of odd tasks; these can be cleaning, walking the dog, or even purchasing an even amount n of CDs where n is equal to the square root of 289. But then the lost bet thought experiment is actually not so logical after all because hidden within is the impossibility of a number n being even and the square root of 289: it’s just not possible in any logical world. Somewhere in the Evil Genius Thought Experiment may be hidden a contradiction to any logical world. The Evil Genius World may not be so logically possible after all, leading to the eventual downfall of Descartes argument because it relies heavily on a conceivability argument, and that does not guarantee logical possibility.
Comment: “This is very good exposition, Adela.” Oh goodness, I feel elated!!! (:
