2
THE NATURAL HISTORY OF THE COMMON CRAYFISH.
for
the commonest purposes
of eve^da}^ existence.
Common sense is science exactly in so far as it fulfils the ideal of common sense ; that is, sees facts as they are, or, at any rate, without the distortion of prejudice, and reasons from them in accordance with the dictates of sound judgment. And science is simply common sense at its best; that is, rigidly accurate in observation, and merciless to fallacy in logic. Whoso will question the validity of the conclusions of sound science, must be prepared to carry his scepticism a long way; for it may be safely affirmed, that there is hardly any
of those decisions
of common sense on
which men stake their all in practical life, which can justify itself so thoroughly on common sense principles, as the broad truths of science can be justified. The conclusion drawn from due consideration of the nature of the case is verified by historical inquiry; and the historian of every science traces back its roots to the primary stock of common information possessed by all mankind. In its earliest development knowledge is self-sown. Impressions force themselves upon men’s senses whether they will or not, and often against their will.
The
amount of interest which these impressions awaken is determined by the coarser pains and pleasures which they carry in their train, or by mere curiosity;
and
reason deals with the materials supplied to it as far as that interest carries it, and no farther.
Such common
