The roots of spirit in matter.
If man were a static or intelligible being, such as angels are
thought to be, his life would have a single guiding interest, under
which all other interests would be subsumed. His acts would explain
themselves without looking beyond his given essence, and his soul would
be like a musical composition, which once written out cannot grow
different and once rendered can ask for nothing but, at most, to be
rendered over again. In truth, however, man is an animal, a portion of
the natural flux; and the consequence is that his nature has a moving
centre, his functions an external reference, and his ideal a true
ideality. What he strives to preserve, in preserving himself, is
something which he never has been at any particular moment. He maintains
his equilibrium by motion. His goal is in a sense beyond him, since it
is not his experience, but a form which all experience ought to receive.
The inmost texture of his being is propulsive, and there is nothing more
intimately bound up with his success than mobility and devotion to
transcendent aims. If there is a transitive function in knowledge and an
unselfish purpose in love, that is only because, at bottom, there is a
self-reproductive, flying essence in all existence ... In order to have
a soul to save he must perpetually form it anew; he must, so to speak,
earn his own living.
GEORGE SANTAYANA, V. REASON IN SOCIETY, I. LOVE 1905-06.