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How do I know that what I clearly and distinctly perceive is true?
1. God exists.
2. God is the ultimate source of these perceptions.
3. God does not deceive.
How do I know that God exists?
1. What I clearly and distinctly perceive is true.
2. I clearly and distinctly perceive that God exists.
‘[F]rom this contemplation of the true God ... I think I can see a way forward to the knowledge of other things. To begin with, I recognize that it is impossible that God should ever deceive me. . . . And since God does not wish to deceive me, he surely did not give me the kind of faculty which would ever enable me to go wrong while using it correctly’
Meditation IV
also: doubt about clear and distinct perception
(e.g. doubt that 2+3=5)
1. It is possible to doubt things that are clearly perceived.
2. We must find justification for removing doubt.
3. Therefore, we must find justification for not doubting what is clearly perceived.
‘what I took just now as a rule, namely that everything we conceive very clearly and very distinctly is true, is assured only for the reasons that God is or exists
, that he is a perfect being, and that everything in us comes from him. It follows that our ideas or notions, being real things and coming from God, cannot be anything but true, in every respect in which they are clear and distinct.’
Discourse on Method
‘I am certain that I am a thinking thing.
Do I not therefore also know what is required for my being certain about anything?
In this first item of knowledge there is simply a clear and distinct perception of what I am asserting; this would not be enough to make me certain of the truth of the matter if it could ever turn out that something which I perceived with such clarity and distinctness was false.’
‘I now seem to be able to lay it down as a general rule that
whatever I perceive clearly and distinctly is true’
Meditation III
God exists therefore clear perceptions are true
or
Clear perceptions are true therefore God exists?
‘I think I can see a way forward to the knowledge of other things ... since God does not wish to deceive me, he surely did not give me the kind of faculty which would ever enable me to go wrong while using it correctly’
Meditation IV
‘there arises in me a clear and distinct idea of a being who is independent and complete, that is, an idea of God.
And from the mere fact that there is such an idea within me [...] I clearly infer that God also exists [...]
So clear is this conclusion that I am confident that the human intellect cannot know anything that is more evident or more certain.’
Meditation VI
1. If we can know anything, then we can know God exists.
2. We can know something.
3. Therefore, we can know God exists.
4. But God doesn’t deceive us.
5. Therefore what we clearly perceive is true.
Two Interpretations
1. The sciences need a metaphysical foundation.
2. This foundation must include a refutation of scepticism.
‘I had seen many ancient writings by the Academics and Sceptics on this subject, and was reluctant to reheat and serve this precooked material’
Second Replies
1. The assumption that sensory perception enables us to know the essential nature of things leads to bad science.
2. Reflection on possible grounds for doubt provides reasons to reject this assumption.
If Descartes were refuting scepticism, the Cartesian Circle would be inescapable.
But it isn’t.
So Descartes isn’t refuting scepticism.
... or?
’an atheist can be clearly aware that the three angles of a triangle are equal to two right angles [...]. But I maintain that this awareness of his is not true knowledge, since no act of awareness that can be rendered doubtful seems fit to be called knowledge’
Second Replies