14. III. Sensitive knowledge of the particular existence of finite beings without us.
These two, viz., intuition and
demonstration, are the degrees of our knowledge; whatever comes short of one of these, with what assurance
soever embraced, is but faith or opinion, but not knowledge, at least in all general truths. There is, indeed, another
perception of the mind, employed about the particular existence of finite beings without us, which, going beyond
bare probability, and yet not reaching perfectly to either of the foregoing degrees of certainty, passes under the
name of knowledge. There can be nothing more certain than that the idea we receive from an external object is in
our minds: this is intuitive knowledge. But whether there be anything more than barely that idea in our minds;
whether we can thence certainly infer the existence of anything without us, which corresponds to that idea, is that
whereof some men think there may be a question made; because men may have such ideas in their minds, when
no such thing exists, no such object affects their senses. But yet here I think we are provided with an evidence that
puts us past doubting. For I ask any one, Whether he be not invincibly conscious to himself of a different
perception, when he looks on the sun by day, and thinks on it by night; when he actually tastes wormwood, or
smells a rose, or only thinks on that savour or odour? We as plainly find the difference there is between any idea
revived in our minds by our own memory, and actually coming into our minds by our senses, as we do between
any two distinct ideas. If any one say, a dream may do the same thing, and all these ideas may be produced in us
without any external objects; he may please to dream that I make him this answer:--1. That it is no great matter,
whether I remove his scruple or no: where all is but dream, reasoning and arguments are of no use, truth and
knowledge nothing. 2. That I believe he will allow a very manifest difference between dreaming of being in the
fire, and being actually in it. But yet if he be resolved to appear so sceptical as to maintain, that what I call being
actually in the fire is nothing but a dream; and that we cannot thereby certainly know, that any such thing as fire
actually exists without us: I answer, That we certainly finding that pleasure or pain follows upon the application
of certain objects to us, whose existence we perceive, or dream that we perceive, by our senses; this certainty is as
great as our happiness or misery, beyond which we have no concernment to know or to be. So that, I think, we
may add to the two former sorts of knowledge this also, of the existence of particular external objects, by that
perception and consciousness we have of the actual entrance of ideas from them, and allow these three degrees of
knowledge, viz., intuitive, demonstrative, and sensitive: in each of which there are different degrees and ways of
evidence and certainty.