phenomena._ In all the respects here
noted, science may be contrasted with those matters of _common
knowledge_, of _opinion_ or _belief_ which are the fruit of our
casual daily thinking and experience. Science is, in the first
place, a body of _systematized_ knowledge. One has but to
contrast the presentation of facts in an ordinary textbook in
zooelogy with the random presentation of facts in a newspaper
or in casual conversation. In science the facts bearing on a
given problem are presented as completely as possible and
are classified with reference to their significant bearings upon
the problem. Moreover the facts gathered and the classifications
of relationship made are not more or less accurate, more
or less true; they are tested and verified results. That
putrefaction, for example, is due to the life of micro-organisms in
the rotting substance is not a mere assumption. It has been
proved, tested, and verified by methods we shall have occasion
presently to examine.

Scientific knowledge, moreover, is general knowledge. The
relations it expresses are not _true_ in some cases of the precise
kind described, _untrue_ in others. The relations hold true
whenever these precise phenomena occur. This generality
of scientific relations is closely connected with the fact that
science expresses relations of exactly defined phenomena.
When a scientific law expresses a certain relation between _A_
and _B_, it says in effect: Given _A_ as meaning this particular
set of conditions and no others, and _B_ as meaning this particular
set of conditions and no others, then this relation holds
true. The relations between _exactly_ defined phenomena
are expressed in general terms, that is, the relations expressed
hold true, given certain conditions, whatever be the accompanying
circumstances. It makes no difference what be the
kind of objects, the law of gravitation still holds true: the
attraction between objects is directly proportional to the product
of their masses and inversely proportional to the square
of the distance between them.

Thus science as an activity is marked off by its method and
its intent rather than by its subject-matter. As a method it
is characterized by thoroughness, persistency, completeness,
generality, and system. As regards its intent, it is characterized
by its freedom from partiality or prejudice, and its interest
in discovering what the facts are, apart from personal
expectations and desires. In the