method by which man has progressed from the life
of the cave man to the complicated industrial civilization of
to-day. Bergson writes in this connection:

As regards human intelligence, it has not been sufficiently noted
that mechanical invention has been from the first its essential
feature, that even to-day our social life gravitates around the
manufacture and use of artificial instruments, that the inventions which
strew the road of progress have also traced its direction. This we
hardly realize, because it takes us longer to change ourselves than to
change our tools. Our individual and even social habits survive a
good while the circumstances for which they were made, so that the
ultimate effects of an invention are not observed until its novelty
is already out of sight. A century has elapsed since the invention of
the steam engine, and we are only just beginning to feel the depths
of the shock it gave us. But the revolution it has effected in industry
has nevertheless upset human relations altogether. New ideas
are arising, new feelings are on the way to flower. In thousands of
years, when, seen from the distance, only the broad lines of the
present age will still be visible, our wars and our revolutions will count
for little, even supposing they are remembered at all; but the steam
engine and the procession of inventions that accompanied it, will
perhaps be spoken of as we speak of the bronze or of the chipped
stone of prehistoric times: it will serve to define an age. If we could
rid ourselves of all pride, if, to define our species, we kept strictly to
what the historic and the prehistoric periods show us to be the
constant characteristic of man and of intelligence, we should not say
_Homo sapiens_, but _Homo faber_.[1]

[Footnote 1: Bergson: _Creative Evolution_, pp. 138-39.]

Man's intelligence, it has so often been said, enables him to
control Nature, but his intelligence in the control of natural
resources is dependent for effectiveness on adequate material
instruments. One may subscribe, though with qualification,
to Bergson's further statement, that "intelligence, considered
in what seems to be its original feature, is the faculty of
manufacturing artificial objects, especially tools to make
tools, and of indefinitely varying the manufacture."

Anthropologists distinguish the prehistoric epochs, by such
terms as the Stone, Copper or Bronze, and Iron Ages, meaning
thereby to indicate what progress man