— 536 —
Sensitive Knowledge of particular Existence.
      §14. These two, (viz.) Intuition and Demonstration, are the
degrees of our Knowledge; whatever comes short of one of these,
— 537 —
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, employ’d about the particular
existence of finite Beings without us; which going beyond bare
probability, and yet not reaching perfectly to either of the fore-
going 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 Know-
ledge. But whether there be any thing more than barely that Idea in
our Minds, whether we can thence certainly inferr the existence
of any thing 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 ’tis 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
— 538 —
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.
Locke Hum IV, 2, §14, pp. 536-537-538