1. General Propositions that are certain concern not Existence.
HITHERTO we have only considered the essences of things; which being
only abstract ideas, and thereby removed in our thoughts from particular
existence, (that being the proper operation of the mind, in abstraction,
to consider an idea under no other existence but what it has in the
understandings,) gives us no knowledge of real existence at all. Where,
by the way, we may take notice, that universal propositions of whose
truth or falsehood we can have certain knowledge concern not existence:
and further, that all particular affirmations or negations that would
not be certain if they were made general, are only concerning existence;
they declaring only the accidental union or separation of ideas in
things existing, which, in their abstract natures, have no known
necessary union or repugnancy.
2. A threefold Knowledge of Existence.
But, leaving the nature of propositions, and different ways of
predication to be considered more at large in another place, let us
proceed now to inquire concerning our knowledge of the EXISTANCE OF
THINGS, and how we come by it. I say, then, that we have the knowledge
of OUR OWN existence by intuition; of the existence of GOD by
demonstration; and of OTHER THINGS by sensation.
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.