eliminate from objective reality
everything that it is not necessary to know in order to utilize objects
for the purpose of preserving life. In complete darkness an animal, if
it does not perish, ends by becoming blind. Parasites which live in the
intestines of other animals upon the nutritive juices which they find
ready prepared for them by these animals, as they do not need either to
see or hear, do in fact neither see nor hear; they simply adhere, a kind
of receptive bag, to the being upon whom they live. For these parasites
the visible and audible world does not exist. It is enough for them that
the animals, in whose intestines they live, see and hear.

Knowledge, then, is primarily at the service of the instinct of
self-preservation, which is indeed, as we have said with Spinoza, its
very essence. And thus it may be said that it is the instinct of
self-preservation that makes perceptible for us the reality and truth of
the world; for it is this instinct that cuts out and separates that
which exists for us from the unfathomable and illimitable region of the
possible. In effect, that which has existence for us is precisely that
which, in one way or another, we need to know in order to exist
ourselves; objective existence, as we know it, is a dependence of our
own personal existence. And nobody can deny that there may not exist,
and perhaps do exist, aspects of reality unknown to us, to-day at any
rate, and perhaps unknowable, because they are in no way necessary to us
for the preservation of our own actual existence.

But man does not live alone; he is not an isolated individual, but a
member of society. There is not a little truth in the saying that the
individual, like the atom, is an abstraction. Yes, the atom apart from
the universe is as much an abstraction as the universe apart from the
atom. And if the individual maintains his existence by the instinct of
self-preservation, society owes its being and maintenance to the
individual's instinct of perpetuation. And from this instinct, or rather
from society, springs reason.

Reason, that which we call reason, reflex and reflective knowledge, the
distinguishing mark of man, is a social product.

It owes its origin, perhaps, to language. We think articulately--_i.e._,
reflectively--thanks to articulate language, and this language arose out
of the need of communicating our thought to our neighbours. To think is
to talk with oneself, and each one of us talks with