, to wit, indefinite continuance of action until interfered with.
This is a modification of Newton's "law of continuance," which, with the
other primary laws of motion, must be taken as the foundation of biology
as well as of astronomy.[11-1]

The diminution or dispersion of organic motion is expressed in
physiological terms as _waste_; we are admonished of waste by _pain_;
and thus admonished we supply the waste or avoid the injury as far as we
can. But this connection of pain with waste is not a necessary one, nor
is it the work of a _Providentia particularis_, as the schoolmen said.
It is a simple result of natural selection. Many organisms have been
born, no doubt, in which waste did not cause pain; caused, perhaps,
pleasure. Consequently, they indulged their preferences and soon
perished. Only those lived to propagate their kind in whom a different
sensation was associated with waste, and they transmitted this
sensitiveness increased by ancestral impression to their offspring. The
curses of the human race to-day are alcohol, opium and tobacco, and they
are so because they cause waste, but do not immediately produce painful
but rather pleasurable feelings.

Pain, as the sensation of waste, is the precursor of death, of the part
or system. By parity of evolution, pleasure came to be the sensation of
continuance, of uninterrupted action, of increasing vigor and life.
Every action, however, is accompanied by waste, and hence every pleasure
developes pain. But it is all important to note that the latter is the
mental correlative not of the action but of its cessation, not of the
life of the part but of its ceasing to live. Pain, it is true, in
certain limits excites to action; but it is by awakening the
self-preservative tendencies, which are the real actors. This
physiological distinction, capable of illustration from sensitive
vegetable as well as the lowest animal organisms, has had an intimate
connection with religious theories. The problems of suffering and death
are precisely the ones which all religions set forth to solve in theory
and in practice. Their creeds and myths are based on what they make of
pain. The theory of Buddhism, which now has more followers than any
other faith, is founded on four axioms, which are called "the four
excellent truths." The first and fundamental one is: "Pain is
inseparable from existence." This is the principle of all pessimism,
ancient and modern. Schopenhauer, an out-and-out p