Descartes' Substance Dualism

Where does Descartes write about substance dualism?

"Meditations" and "The Passion of the Soul"

What is Descartes method?

- Hyperbolic doubt (extreme scepticism) -> doubting everything he knows to discern whether anything can be known with certainty

- Rejects anything he knows if there is any doubt of their certain truth -> establish which beliefs have endurance + stability

- Notes how senses can be mistaken (e.g refraction of a straw in water) -> speculates if they are misled by a demon

- Leads to a natural division between the body + the soul

What does Descartes conclude about the senses and certainty?

- The whole material world may be illusionary/a dream

- The only knowledge he cannot doubt is that he is thinking sceptically (the cogito)

- We have a mind (but no conclusion about whether we have a body)

What is the cogito?

I think therefore I am (no experience if we weren't thinking -> as long as we think, we exist)

What did Descartes' method lead him to?

Privilege the mental over the (doubtable) material -> mind + body are different substances

Why might Descartes method be criticised?

Prioritises the mind/mental over the body (empiricism + physical experience)

What law does Descartes follow?

Leibniz's law

What is Leibniz's law?

For 2 substances to be the same, they must have the same properties

What does Descartes argue about the mind and the body?

They cannot be the same because they have different properties (are non-identical)

What is an essential property of a physical substance?

Extension

What can physical substances be because they have extension?

Divided

What is the body (according to Descartes)?

- Material

- Performs physical activities observable to all

- Describable in terms of extension -> time, space, depth etc

- It is divisible -> consists of many parts (e.g limbs)

What is the mind (according to Descartes)?

- Has no place in the spatio-temporal world

- Place of thought, feelings + sensations of everything that cannot be physically located

- Only known by the person experiencing it

- Indivisible (cannot be split into parts) -> seems to be non-extended + isn't located in space

Why is it possible for the mind to be separate from the body and, therefore, be non-identical?

The mind is non-extended so it is possible to conceive of it without any extended thing (e.g imagine being an immaterial ghost walking through walls)

What did Descartes say about divisibility?

"The body by nature is divisible, but the mind is not"

How does Descartes describe the soul and the body in Meditation VI?

Soul as the pilot of the body + the body is a sort of mechanism

Can the mind and body interact with each other?

Yes

How can the mind and the body interact with each other?

In the pineal gland

What is the pineal gland?

- Small gland located at the centre of the brain, in between hemispheres

- Control centre from which the soul moves the limbs

- Produced melatonin (hormone regulating)

Why does Descartes conclude that the intersection between the mind and the body is located in the pineal gland?

- It is a singularity + indivisible

- Everything else in the body comes in pairs (e.g eyes, ears, hemispheres)

What are the strengths of Descartes' substance dualism?

- Based on reason (not empiricism where senses may not always be trusted) -> lead to more logical certainties (however this moves from what we know to an area we know nothing about)

- Solves Plato's issue of interaction between the soul + the body -> they have an intersection (to an extent)

What are the problems with Descartes' substance dualism?

- Does not explain how the pineal gland creates the link between the body + the brain + there is no evidence (conversion of mental into physical) or why it has to be a singularity

- The mind can be divided into perception, memory, emotions etc BUT Descartes -> mind = consciousness -> perception etc are different modes of consciousness

- Masked man fallacy -> we can conceive the impossible due to ignorance (e.g robber who is our dad) -> not allowing the things we think we know to be doubtable (don't allow for the fact that they might be wrong) -> just because we can't conceive that we don't have a soul doesn't mean we don't have it

- Dawkins -> consciousness is the culmination of an evolutionary trend towards the emancipation of survival machines as executive decision-takers from their ultimate masters, the genes (genes are the basic units of selfishness)

- Anscombe -> "this bodily act is an act of a man qua spirit" (act of pointing) -> the act of a human as a whole (not separate)

- 2nd law of thermodynamics (conservation of energy principle) -> soul comes from somewhere + can affect the physical (not scientific) -> energy is transformed into matter and vice versa

- Minds perception of itself is not accurate or complete (makes assumption) -> neuroscience + psychology shows that we are ignorant about our minds (e.g most processes are unconscious so we are not aware of their occurrence)

- Geach -> "man is a sort of body, not a body plus an immaterial somewhat" "thinking is a vital activity of man, not any part of him, immaterial or material"

What is G.Ryle's criticism of Descartes' substance dualism?

- "No ghost in the machine"

- Category error by assuming that mind + matter are of the same logical type (both names of things) + that sensations/events must be either mental or physical (can be both)

- E.g being shown around the different parts of Cambridge + then asking "but where is the university" -> collectively make up the uni

- The whole is made up of the parts/isn't separable from the parts -> can't separate the mental from the physical