Descartes on Doubt

What's the method?

- how do we challenge the authority of the five senses?

- the way to do this is via systematic doubt: demolish everything and start again.

- snippets:

Why doubt?

- many beliefs that we have inherited from childhood have never been tested.

- the senses are often seen as the foundation for our knowledge, but the senses can sometimes deceive us.

- yet some things seem beyond doubt, such that my body is mine. How could I deny this? To do so would be madness. So, he's aware of how counter-intuitive this whole project might seem to be.

- (note that Descartes is addressing himself to people who do believe all knowledge comes via the senses, and he thinks that most people naturally think this; it's the plausible thing to think.)

The Dream Argument

- snippets:

- Can we really tell the difference between being awake and dreaming?

? ? Yes: they are phenomenologically quite different experiences.

? ? Response: we can only say that after we have woken up. What about when we are dreaming? (Have you ever dreamt that you woke up from a dream?)

? ? Can we be absolutely sure that we are not dreaming right now?

- Objection: dreams are made out of components that come from the senses (objects, colours), so ti cannot all be a dream

? ? Reply: the most basic things presupposed -- concept of a body, physical extension, number, time, etc. -- might not come via the senses.

Gods and Demons

- If God exists, perhaps he:

????i) continually deceives me about the nature of the external world, or

????ii) created me impefectly so that I often make mistakes?

- If God does not exist, I am definitely not created perfectly, and so I am bound to make mistakes. (Evolution might attune us to some truths, but not others.)

- Imagine a malicious demon who continually deceives me; how could I know that I am being deceived? If I imagine this, I will have to assume that nothing is as it seems.

- snippets:

Descartes' Method

- Descartes wants to undermine unthinking belief in the reliability of the senses.

- He admits that we all naturally believe the testimony of the senses.

- So he tries to counter-balance that natural belief with an extreme alternative ('everything might be a dream or illusion')

- The aim is to generate doubt and suspension of judgement, drawing on the Pyrrhonian scepticism of Sextus Empiricus (and the sceptical tradition in France: e.g. Montaigne).

- Opposed beliefs leads to equipollence, which generates suspension of judgement.

- The doubt is not 'the external world is just a dream', but rather 'perhaps the senses are not as trustworthy as they seem'.

- Therefore, we need a new foundation for our knowledge, independent of the senses, that is beyond all doubt.

- counter-balance snippets:

What is Pyrrhonism?

- A pair of two opposed beliefs generate a state of 'equipollence' (balance)

? ? This balance leads to confusion and, ultimately, suspension of judgement.

- Sextus Empiricus, Outlines of Pyrrhonism:

? ? Scepticism is "the ability to set in opposition appearances and ideas in any manner whatsoever, the result of which is first that, because of the equal force of the opposed objects and arguements, final suspension of judgement is achieved, and then freedom of disturbance".

Senses vs. Reason

- The senses seem to show that the sun moves across the sky, while the earth is still.

? ? Is this the senses deceiving us?

? ? When we learn that the sun is still and the earth is in fact moving, is this reason corrrecting the senses, or is it further sensory information amending our first impression?

- Fifth Objections (Gassendi): error is the product of our judgements, not the senses.

- Sixth Replies: but it is reason that corrects the errors of the senses.

? ? Do errors come from reason or the senses?

? ? At this stage, Descartes doesn't need to answer this question. He just wants to show that we are sometimes mistaken in cases where we think we are certain (Fifth Replies).

- snippets:

????- Fifth Objections (Gassendi)

????- Descartes, Sixth Replies

????- Fifth Replies (to Gassendi)

Questions

- Is there any way to distinguish between dreaming and being awake?

- Could you ever doubt the existence of your own body?

- Could God or an evil demon deceive me into thinking that 2 + 2 = 5 ?

- The sun appears to move and the earth appears still; is this deception by the senses or by reason (i.e. our judgement)?

- Does Descartes successfully undermine our entirely natural trust in the senses?

- In the debate between Descartes and Gassendi, who do you think is most convincing?