ons. I shall omit this line of
argument, which I have developed elsewhere.* For the moment I will
content myself with saying that the powers of logic seem to me very
much less than this theory supposes. If it were taken seriously, its
advocates ought to profess that any one truth is logically inferable
from any other, and that, for example, the fact that Caesar conquered
Gaul, if adequately considered, would enable us to discover what the
weather will be to-morrow. No such claim is put forward in practice, and
the necessity of empirical observation is not denied; but according to
the theory it ought to be.

* In the article on "The Monistic Theory of Truth" in
"Philosophical Essays" (Longmans, 1910), reprinted from the
"Proceedings of the Aristotelian Society," 1906-7.

Another objection is that no endeavour is made to show that we cannot
form a consistent whole composed partly or wholly of false propositions,
as in a novel. Leibniz's conception of many possible worlds seems to
accord much better with modern logic and with the practical empiricism
which is now universal. The attempt to deduce the world by pure thought
is attractive, and in former times was largely supposed capable of
success. But nowadays most men admit that beliefs must be tested by
observation, and not merely by the fact that they harmonize with other
beliefs. A consistent fairy-tale is a different thing from truth,
however elaborate it may be. But to pursue this topic would lead us
into difficult technicalities; I shall therefore assume, without further
argument, that coherence is not sufficient as a definition of truth.

III. Many difficult problems arise as regards the verifiability of
beliefs. We believe various things, and while we believe them we think
we know them. But it sometimes turns out that we were mistaken, or at
any rate we come to think we were. We must be mistaken either in our
previous opinion or in our subsequent recantation; therefore our beliefs
are not all correct, and there are cases of belief which are not cases
of knowledge. The question of verifiability is in essence this: can we
discover any set of beliefs which are never mistaken or any test which,
when applicable, will always enable us to discriminate between true
and false beliefs? Put thus broadly and abstractly, the answer must be
negative. There is no way hitherto discovered of wholly eliminating the
risk of error, and no infallible criterion. If we be