3. Our knowledge of our own existence is intuitive.
As for our own existence, we perceive it so plainly and so
certainly, that it neither needs nor is capable of any proof. For nothing can be more evident to us than our own
existence. I think, I reason, I feel pleasure and pain: can any of these be more evident to me than my own
existence? If I doubt of all other things, that very doubt makes me perceive my own existence, and will not suffer
me to doubt of that. For if I know I feel pain, it is evident I have as certain perception of my own existence, as of
the existence of the pain I feel: or if I know I doubt, I have as certain perception of the existence of the thing
doubting, as of that thought which I call doubt. Experience then convinces us, that we have an intuitive
knowledge of our own existence, and an internal infallible perception that we are. In every act of sensation,
reasoning, or thinking, we are conscious to ourselves of our own being; and, in this matter, come not short of the
highest degree of certainty.