Substance dualism Flashcards
what is Descartes’ substance dualism?
Descartes’ substance dualism is the theory that there are two distinct substances, mental and physical. The essence of mental substance is thinking, the essence of physical substance is extension. A thing is extended if it takes up physical space, is located, has coordinates.
what is a substance?
A substance is a fundamental type of existence which can’t be broken down into anything else.
the indivisibility argument (Descartes)
Anything that is extended in space can be divided, because there has to be some point along which it could conceivably be divided. The mind does not appear to be divisible, however, because it seems to be non-extended. The mind is not located in space; it does not have spatial coordinates along which it could be divided.
Leibniz’ law is that identical things must have the same properties. The physical has the property of being divisible but the mental does not. If the body and mind were identical, then that one identical thing would be both divisible and indivisible, which is impossible. Therefore, the mind and body are not identical.
indivisibility argument standard form
P1. Physical substance is divisible (since it’s extended).
P2. The mind is indivisible (since it’s non-extended).
P3. Leibniz’ law is that identical things must have the same properties.
C1. The mind therefore cannot be identical with any physical substance, such as the body.
issues of indivisibility (the mental is divisible)
The mind can be divided into perception, memory, emotions and so on. So, the mind and body share the same property of divisibility and thus could be identical.
in cases of mental illness such as DID
attacks P2, the premise that the mind is indivisible, in which case the mind does have the same properties as the physical body, making the indivisibility argument false.
Discoveries in modern science can be used to push the objection further and tackle Descartes’ account of the mind as consciousness head on. There are phenomena which have been discovered by modern psychology which could suggest that actual divisions of the mind are possible, e.g. blindsight & separated brain hemispheres. The brain is split into two hemispheres which are only connected by a thin strand of neurons called the corpus collosum, which can sometimes be cut as a medical procedure to treat epilepsy. This has the bizarre effect of, some have argued, seeming to result in two separate ‘persons’ in the one body. The right hemisphere controls the left arm and the left hemisphere the right arm. Patients have been observed picking up some food with one arm and the other arm hitting it away. One case involved a patient who tried to hug his wife with one arm and push her away with the other.
issues of indivisibility (physical is not always divisible)
Quarks are what neutrons and protons are made up of. Quarks are elementary particles, meaning they are not made up of smaller particles. They are fundamental; they cannot be broken down into anything smaller. This means they are indivisible.
force fields are indivisible yet physical
Descartes conceivability argument
Since the mind is non-extended, it is possible to conceive of it without any extended thing, existing independently of anything physical. For example, you could imagine being an immaterial ghost walking through walls.
If two things are actually identical, then they cannot possibly be separate. E.g., a triangle cannot possibly be sperate from having three sides. The separability of two identical things is not even conceivable. E.g., we cannot conceive of a triangle without three sides.
So, since we can conceive of the mind without the body it follows that it is possible for the mind to be separate from the body, from which it follows the mind is actually not identical to the body.
conceivability argument standard form
P1. I have a clear and distinct idea of myself as a thinking non-extended thing.
P2. I have a clear and distinct idea of my body as a non-thinking extended thing.
C1. These opposing properties allow us to conceive of the mind separate to and without the body.
P3. What is conceivably separate is possibly separate.
P4. What is possibly separate is actually non-identical.
C2. Therefore, the mind and body are not identical.
