We may thus seem to be landed in a howling wilderness of scientific
uncertainty. The result of pushing our inquiries so far may seem to be
to show that we really know nothing at all. But in truth the uncertainty
is no greater than the uncertainty which attends all inquiries in the
historical sciences. Though a historical fact may be recorded in the
most trustworthy documents, though it may have happened in our own
times, though we may have seen it happen with our own eyes, yet we
cannot have the same certainty about it as the mathematician has about
the proposition which he proves to absolute demonstration. We cannot
have even that lower degree of certainty which the geologist has with
regard to the order of succession between this and that _stratum_. For
in all historical inquiries we are dealing with facts which themselves
come within the control of human will and human caprice, and the
evidence for which depends on the trustworthiness of human informants,
who may either purposely deceive or unwittingly mislead. A man may lie;
he may err. The triangles and the rocks can neither lie nor err. I may
with my own eyes see a certain man do a certain act; he may tell me
himself, or some one else may tell me, that he is the same man who did
some other act; but as to his statement I cannot have absolute
certainty, and no one but myself can have absolute certainty as to the
statement which I make as to the facts which I saw with my own eyes.
Historical evidence may range through every degree, from the barest
likelihood to that undoubted moral certainty on which every man acts
without hesitation in practical affairs. But it cannot get beyond this
last standard. If, then, we are ever to use words like race, family, or
even nation, to denote groups of mankind marked off by any kind of
historical, as distinguished from physical, characteristics, we must be
content to use those words, as we use many other words, without being
able to prove that our use of them is accurate, as mathematicians judge