A morality, to justify itself, must appeal to
the heart of man. The good which it recommends must be
a good which man can without sophistry approve. And the
good for which man can whole-heartedly strive is not determined
by logic, but, in the last analysis, by biology. Human
beings cannot freely call good that to which they have no
spontaneous prompting. Those ascetics who have denied
the flesh may have displayed a certain degree of heroism, but
they displayed an equal lack of insight. For it is out of
physical impulses alone that any ideal values can arise.

It is only when one instinct interferes with its neighbors,
or one individual with his fellows, that instincts or activities
can be called evil. They are called evil in relation, in
context, with reference to their consequences. In itself no
natural impulse is subject to condemnation. It is just as
natural as thunder or sunshine, and is to be taken as a point
of departure, as a basis for action, rather than as a chance
for censure. Impulses demand control simply because, left
to themselves, they collide with each other, just as individuals
uncontrolled by custom, law, and education, collide
with each other in the pursuit of satisfaction. The ideal is
a way of life, which will allow as much spontaneity as the
conditions of nature and life allow, and provide as much control
as they make necessary. To be thus in control of one's
desires is to be free. It is to utilize one's interests and capacities
in the light of a harmony both of one's own desires, and
in so far as this harmony is universal, of the desires of all men.
It is to lead the Life of Reason:

Every one leads the Life of Reason in so far as he finds a steady
light behind the world's glitter, and a clear residuum of joy beneath
pleasure and success. No experience not to be repented of falls
without its sphere. Every solution to a doubt, in so far as it is not
a new error, every practical achievement not neutralized by a second
maladjustment consequent upon it, every consolation not the seed
of another, greater sorrow, may be gathered together and built into
this edifice. The Life of Reason is the happy marriage of two
elements--impulse and ideation--which if wholly divorced would
reduce man to a brute or to a maniac. The rational animal is
generated by the union of these two monsters. He is constituted by
ideas which have ceased to be visionary and actions which have
ceased to be vain.[1]

[Footnote