Descartes on Dualism

Material Things

- The was example showed us that the essense of material bodies is extension. That's the one unchanging property that persists through all other changes.

- Mathematics,?in particular, geometry - reasons about extended entities.

- If I can conceive three-dimensionally extended objects clearly and distinctly, then it is at least possible that they could exist. They involve no contradiction, and God certainly has the power to make them exist.

Human Faculties

- Before tackling the existence of material things directly, Descartes reflects on the differences between three human faculties: understanding, imagination, and then perception.

- I can understand geometrical objects and I can also imagine them.

- I can understand the idea of triangle, and I can visualize a triangle. I can also understand the idea of a chiliagon (a polygon with 1000 sides), but I cannot visualize it. This shows that understanding and imagination are distinct faculties.

- While understanding is part of my essence as a thinking thing, imagination is not (for I could still think without it).

- If the imagination is a non-essential part of me, and can visualize material bodies, then it is posible that it is part of my material body, and so it seems plausible to suggest that the body exists.

Perception

- We have no control over our perceptions; therefore, it is reasonable to suppose that they are caused by sth. external to us.

- Like imagination, perception seems closely tied to the body, and not part of myself as a thinking thing.

- Both perception and imagination, which are distinct from the understanding, give reasons to believe (although not a firm proof) that bodies exists.

- If we have these faculties that are not part of our essential selves as thinking things, that might suggest that we are in some way attached to sth. else where these faculties reside (i.e. our bodies).

Distinction between mind & body

Descartes' Argument

- I know that I am a thinking thing.

- I have a distinct idea of body (i.e. extended substance).

- My existence as a thinking thing does not depend on the existence of a body.

- Therefore, there must be two distinct substances, mind and body.

- I cannot distinguish parts within myself as a thinking thing, but I can divide any body into parts. (This is because the latter is spatially extended, but the former is not.) This shows that mind and body are fundamentally different in kind; i.e. they are different substances.

The Existence of Bodies

- I perceive things "without my cooperation and often against my will", so there must be a substance distinct from me that exists.

- The only substances I have ideas of apart from myself as a thinking substance are:

????i) God,?

????ii) body or extended substance.

- It would be deceptive of God to create the impression of a world of existing bodies that were not really there. (A malicious demon might do that, but not God.)

- Therefore, body must exist.

God not deceptive

Mind and Body Reunited

- Now that we know that body (extended substance) exists, and that God is not deceiving us, we can turn again to what the senses show us.

- They show that we are embodied creatures, a unity of mind and body.

- We no longer have good grounds to doubt this.

But what about misleading senses?

- The senses are designed to aid in our preservation, to show us what will benefit or harm us.

- Whenever the senses mislead us, it is because they are calibrated to help protect us, not to show us the nature of things in themselves.

- The fire is not really hot (that's a secondary quality, part of our subjective experience), but it is useful to think it is hot in order to avoid getting burnt.

- So, although the senses are in general reliable - they accurately present a spatially extended world that exists - they can also mislead us in certain respects.

- This is due to our finite nature as human beings, both limited in abilities but also motivated by needs of self-preservation.

- Once we know this, we can correct for mistakes we might make.

Misleading Senses

The Argument of the Meditations

- I eixst as a thinking thing.

- Some thoughts (i.e. perceptions) are forced upon me from outside and could not have been generated by myself.

- Therefore, sth. else exists apart from me.

- My idea of God as a perfect being and the very idea of a perfect being both make it necessary that God exists.

- My perceptions present to me a spatially extended material world.

- God, as a perfect being, would not deceive me.

- Therefore, the spatially extended world of bodies exist.

- We can explain why the senses are sometimes misleading without udnermining their general reliability. Scepticism is defeated.

Questions

- What arguments does Descartes use to make the claim that the mind (thinking substance) and body (extended substance) are distinct?

- Do you agree with Descartes that the mind and body are fundamentally different in kind, two distinct types of thing?

- If so, do you think that the mind can exist without a body?

- Thinking about Descartes' project as a whole, what does Descartes think we have gained by going through this process?

- Was the journey worth the effort just to get back to where we began? What, if anything, have we gained along the way?