. We have first an expectation, then a sensation
with the feeling of expectedness related to memory of the expectation.
This whole experience, when it occurs, may be defined as verification,
and as constituting the truth of the expectation. Appropriate action,
during the period of expectation, may be regarded as additional
verification, but is not essential. The whole process may be illustrated
by looking up a familiar quotation, finding it in the expected words,
and in the expected part of the book. In this case we can strengthen
the verification by writing down beforehand the words which we expect to
find.

I think all verification is ultimately of the above sort. We verify a
scientific hypothesis indirectly, by deducing consequences as to the
future, which subsequent experience confirms. If somebody were to doubt
whether Caesar had crossed the Rubicon, verification could only be
obtained from the future. We could proceed to display manuscripts to our
historical sceptic, in which it was said that Caesar had behaved in this
way. We could advance arguments, verifiable by future experience, to
prove the antiquity of the manuscript from its texture, colour, etc. We
could find inscriptions agreeing with the historian on other points,
and tending to show his general accuracy. The causal laws which our
arguments would assume could be verified by the future occurrence of
events inferred by means of them. The existence and persistence of
causal laws, it is true, must be regarded as a fortunate accident, and
how long it will continue we cannot tell. Meanwhile verification remains
often practically possible. And since it is sometimes possible, we
can gradually discover what kinds of beliefs tend to be verified by
experience, and what kinds tend to be falsified; to the former kinds
we give an increased degree of assent, to the latter kinds a diminished
degree. The process is not absolute or infallible, but it has been
found capable of sifting beliefs and building up science. It affords
no theoretical refutation of the sceptic, whose position must remain
logically unassailable; but if complete scepticism is rejected, it gives
the practical method by which the system of our beliefs grows gradually
towards the unattainable ideal of impeccable knowledge.

IV. I come now to the purely formal definition of the truth or falsehood
of a belief. For this definition it is necessary first of all to
consider the derivation of the objective r