ference between a
mechanism which engages the attention and a mechanism from which it can
be diverted. The primitive steam-engine, as Newcomen conceived it,
required the presence of a person exclusively employed to turn on and
off the taps, either to let the steam into the cylinder or to throw the
cold spray into it in order to condense the steam. It is said that a boy
employed on this work, and very tired of having to do it, got the idea
of tying the handles of the taps, with cords, to the beam of the engine.
Then the machine opened and closed the taps itself; it worked all alone.
Now, if an observer had compared the structure of this second machine
with that of the first without taking into account the two boys left to
watch over them, he would have found only a slight difference of
complexity. That is, indeed, all we can perceive when we look only at
the machines. But if we cast a glance at the two boys, we shall see that
whilst one is wholly taken up by the watching, the other is free to go
and play as he chooses, and that, from this point of view, the
difference between the two machines is radical, the first holding the
attention captive, the second setting it at liberty. A difference of the
same kind, we think, would be found between the brain of an animal and
the human brain.

If, now, we should wish to express this in terms of finality, we should
have to say that consciousness, after having been obliged, in order to
set itself free, to divide organization into two complementary parts,
vegetables on one hand and animals on the other, has sought an issue in
the double direction of instinct and of intelligence. It has not found
it with instinct, and it has not obtained it on the side of intelligence
except by a sudden leap from the animal to man. So that, in the last
analysis, man might be considered the reason for the existence of the
entire organization of life on our planet. But this would be only a
manner of speaking. There is, in reality, only a current of existence
and the opposing current; thence proceeds the whole evolution of life.
We must now grasp more closely the opposition of these two currents.
Perhaps we shall thus discover for them a common source. By this we
shall also, no doubt, penetrate the most obscure regions of metaphysics.
However, as the two directions we have to follow are clearly marked, in
intelligence on the one hand, in instinct and intuition on the other, we
are not afraid of straying