experimental fact was so well known to prehistoric man that he
employed this method, as various savage tribes employ it to this day,
for the altogether practical purpose of making a fire; just as he
employed his practical knowledge of the mutability of solids and liquids
in smelting ores, in alloying copper with tin to make bronze, and in
casting this alloy in molds to make various implements and weapons.
Here, then, were the germs of an elementary science of physics.
Meanwhile such observations as that of the solution of salt in water
may be considered as giving a first lesson in chemistry, but beyond such
altogether rudimentary conceptions chemical knowledge could not have
gone--unless, indeed, the practical observation of the effects of fire
be included; nor can this well be overlooked, since scarcely another
single line of practical observation had a more direct influence in
promoting the progress of man towards the heights of civilization.

4. In the field of what we now speak of as biological knowledge,
primitive man had obviously the widest opportunity for practical
observation. We can hardly doubt that man attained, at an early day, to
that conception of identity and of difference which Plato places at
the head of his metaphysical system. We shall urge presently that it
is precisely such general ideas as these that were man's earliest
inductions from observation, and hence that came to seem the
most universal and "innate" ideas of his mentality. It is quite
inconceivable, for example, that even the most rudimentary intelligence
that could be called human could fail to discriminate between living
things and, let us say, the rocks of the earth. The most primitive
intelligence, then, must have made a tacit classification of the natural
objects about it into the grand divisions of animate and inanimate
nature. Doubtless the nascent scientist may have imagined life animating
many bodies that we should call inanimate--such as the sun, wandering
planets, the winds, and lightning; and, on the other hand, he may
quite likely have relegated such objects as trees to the ranks of the
non-living; but that he recognized a fundamental distinction between,
let us say, a wolf and a granite bowlder we cannot well doubt. A step
beyond this--a step, however, that may have required centuries
or millenniums in the taking--must have carried man to a plane of
intelligence from which a primitive Aristotle or Linnaeus was enabled
to not