acter, this last
fruit of human maturity, is but an ideal to which he ought to force his
conformity with a constant vigilance, but to which, with all his efforts,
he can never attain.

He cannot attain to it because his nature is thus made and it will not
change; the physical conditions of his existence themselves are opposed
to it.

In fact, his existence, so far as he is a sensuous creature, depends on
certain physical conditions; and in order to insure this existence man
ought--because, in his quality of a free being, capable of determining
his modifications by his own will--to watch over his own preservation
himself. Man ought to be made capable of certain acts in order to fulfil
these physical conditions of his existence, and when these conditions are
out of order to re-establish them.

But although nature had to give up to him this care which she reserves
exclusively to herself in those creatures which have only a vegetative
life, still it was necessary that the satisfaction of so essential a
want, in which even the existence of the individual and of the species is
interested, should not be absolutely left to the discretion of man, and
his doubtful foresight. It has then provided for this interest, which in
the foundation concerns it, and it has also interfered with regard to the
form in placing in the determination of free arbitration a principle of
necessity. From that arises natural instinct, which is nothing else than
a principle of physical necessity which acts upon free arbitration by the
means of sensation.

The natural instinct solicits the sensuous faculty through the combined
force of pain and of pleasure: by pain when it asks satisfaction, and by
pleasure when it has found what it asks.

As there is no bargaining possible with physical necessity, man must
also, in spite of his liberty, feel what nature desires him to feel.
According as it awakens in him a painful or an agreeable sensation, there
will infallibly result in him either aversion or desire. Upon this point
man quite resembles the brute; and the stoic, whatever his power of soul,
is not less sensible of hunger, and has no less aversion to it, than the
worm that crawls at his feet.

But here begins the great difference: with the lower creature action
succeeds to desire or aversion quite as of necessity, as the desire to
the sensation, and the expression to the external impression. It is here
a perpetual circle, a chain, the links of whic