vital, if we take this word in a descriptive and poetic sense; for
they will contain a movement having a certain idiosyncrasy and taking
a certain time, like the fall of an apple. The movement of nature is
never dialectical; the first part of any event does not logically
imply the last part of it. Physics is descriptive, historical,
reporting after the fact what are found to be the habits of matter.
But if these habits are constant and calculable we call the vitality
of them mechanical. Thus the larger processes of nature, no matter how
vital they may be and whatever consciousness may accompany them, will
always be mechanical if they can be calculated and predicted, being a
combination of the more minute and widespread processes which they
contain. The only question therefore is: Do processes such as
nutrition and reproduction arise by a combination of such events as
the fall of apples? Or are they irreducible events, and units of
mechanism by themselves? That is the dilemma as it appears in science.
Both possibilities will always remain open, because however far
mechanical analysis may go, many phenomena, as human apprehension
presents them, will always remain irreducible to any common
denominator with the rest; and on the other hand, wherever the actual
reduction of the habits of animals to those of matter may have
stopped, we can never know that a further reduction is impossible.

The balance of reasonable presumption, however, is not even. The most
inclusive movements known to us in nature, the astronomical, are
calculable, and so are the most minute and pervasive processes, the
chemical. These are also, if evolution is to be accepted, the earliest
processes upon which all others have supervened and out of which, as
it were, they have grown. Apart from miraculous intervention,
therefore, the assumption seems to be inevitable that the intermediate
processes are calculable too, and compounded out of the others. The