© Michael Lacewing Doubt in Descartes’ Meditations Michael Lacewing

Into doubt We can be deceived by our senses.

Into doubt (2) There are ‘no certain indications by which we may clearly distinguish wakefulness from sleep’.

The cogito I am certain that I think, I exist. I am a thinking thing. But I am not certain I have a body. = ?

The wax argument At first, our idea of the wax is of something defined by its sensory properties. But this is muddled: when I melt a piece of wax, it loses all of its original sensory qualities, yet I believe it is the same wax. This shows our conception of material objects, when clear and distinct, is as changeable and extended.

The external world: two steps to go Meditation V: we can know that clear and distinct ideas are true; so material objects really are extended, if they exist at all. Meditation VI: We have experiences of an external world, which must either be caused by a real external world or God. God is not a deceiver. Therefore material objects do exist.

Clear and distinct ideas On the cogito: ‘In this first item of knowledge there is simply a clear and distinct perception of what I am asserting’. While thinking it, I cannot doubt it. In order to be certain of clear and distinct ideas while we are not considering them, we must first prove God exists.