to the words _cause_ and _effect_; that the _laws of motion_, as they are
at present formulated, do not seem to account satisfactorily for the
behavior of all material particles. From this it is inferred that we
must give up the attempt to explain mechanically the order of physical
things.

Now, suppose that it were considered a dangerous and heterodox doctrine,
that the changes in the system of things are due to the activities of
minds. Would not those who now love to point out the shortcomings of the
science of mechanics discover a fine field for their destructive
criticism? Are there no disputes as to the ultimate nature of mind? Are
men agreed touching the relations of mind and matter? What science even
attempts to tell us how a mind, by an act of volition, sets material
particles in motion or changes the direction of their motion? How does
one mind act upon another, and what does it mean for one mind to act upon
another?

If the science of mechanics is not in all respects as complete a science
as it is desirable that it should be, surely we must admit that when we
turn to the field of mind we are not dealing with what is clear and free
from difficulties. Only a strong emotional bias can lead a man to dwell
with emphasis upon the difficulties to be met with in the one field, and
to pass lightly over those with which one meets in the other.

One may, however, refuse to admit that the order of nature is throughout
mechanical, without taking any such unreasonable position as this. One
may hold that many of the changes in material things do not _appear_ to
be mechanical, and that it is too much of an assumption to maintain that
they are such, even as an article of faith. Thus, when we pass from the
world of the inorganic to that of organic life, we seem to make an
immense step. No one has even begun to show us that the changes that
take place in vegetable and animal organisms are all mechanical changes.
How can we dare to assume that they are?

With one who reasons thus we may certainly feel a sympathy. The most
ardent advocate of mechanism must admit that his doctrine is a working
hypothesis, and not _proved_ to be true. Its acceptance would, however,
be a genuine convenience from the point of view of science, for it does
introduce, at least provisionally, a certain order into a vast number of
facts, and gives a direction to investigation. Perhaps the wisest thing
to do is, not to combat the doctrine, b