ve Logic. But there is a
preliminary and a pendant. Without raising the question of causal
connexion, we are liable to certain errors in ascertaining in what
sequence and with what circumstances events really occurred. These
tendencies to error deserve to be pointed out by way of warning, and
this I shall attempt in a separate chapter on observation of facts
of simple sequence. This is preliminary to the special methods of
observing causal sequence. Then, by way of pendant, I shall consider
two modes of empirical inference from data in which the causal
connexion has not been ascertained or explained--Inference from
approximate generalisations to particular cases, and Inference from
Analogy.

Most of these methods in one form or another were included by Mill
in his system of Inductive Logic, and the great merit of his work was
that he did include them, though at some sacrifice of consistency
with his introductory theory. With regard to the kind of empirical
inference which that theory, following the lead of Whately, took as
the type of all inference, Logic has really little to say. It was this
probably that was in Mill's mind when he said that there is no Logic
of Observation, ignoring the fact that the Experimental Methods are
really methods of observation, as well as the Methods of Eliminating
Chance by calculation of Probability. There is no method of observing
uniformities except simply observing them. Nor indeed is there any
"method" of inferring from them: we can only point out that in
every particular inference from them we assume or postulate their
continuance generally. As regards their observation, we may point
out further that a special fallacy is incident to it, the fallacy of
ignoring exceptions. If we are prepossessed or prejudiced in favour of
a uniformity, we are apt to observe only the favourable instances, and
to be blind to cases where the supposed invariable coincidence does
not occur. Thus, as Bacon remarked among his _Idola_, we are apt to
remember when our dreams come true, and to forget when they do
not. Suppose we take up the notion that a new moon on a Saturday is
invariably followed by twenty days of unsettled weather, one or two
or a few cases in which this notably holds good are apt to be borne in
mind, while cases where the weather is neither conspicuously good
nor bad are apt to be overlooked. But when a warning has been given
against this besetting fallacy, Logic has nothing further to sa