45.  THE PLACE OF MIND IN NATURE.—­One of the very first questions which we think of asking when we contemplate the possibility that the physical world is throughout a mechanical system is this:  How can we conceive minds to be related to such a system?  That minds, and many minds, do exist, it is not reasonable to doubt.  What shall we do with them?

One must not misunderstand the mechanical view of things.  When we use the word “machine,” we call before our minds certain gross and relatively simple mechanisms constructed by man.  Between such and a flower, a butterfly, and a human body, the difference is enormous.  He who elects to bring the latter under the title of mechanism cannot mean that he discerns no difference between them and a steam engine or a printing press.  He can only mean that he believes he might, could he attain to a glimpse into their infinite complexity, find an explanation of the physical changes which take place in them, by a reference to certain general laws which describe the behavior of material particles everywhere.

And the man who, having extended his notion of mechanism, is inclined to overlook the fact that animals and men have minds, that thought and feeling, plan and purpose, have their place in the world, may justly be accused of a headlong and heedless enthusiasm.  Whatever may be our opinion on the subject of the mechanism of nature, we have no right to minimize the significance of thought and feeling and will.  Between that which has no mind and that which has a mind there is a difference which cannot be obliterated by bringing both under the concept of mechanism.  It is a difference which furnishes the material for the sciences of psychology and ethics, and gives rise to a whole world of distinctions which find no place in the realm of the merely physical.

There are, then, minds as well as bodies; what place shall we assign to these minds in the system of nature?

Several centuries ago it occurred to the man of science that the material world should be regarded as a system in which there is constant transformation, but in which nothing is created.  This way of looking at things expressed itself formerly in the statement that, through all the changes that take place in the world, the quantity of matter and motion remains the same.  To-day the same idea is better expressed in the doctrine of the eternity of mass and the conservation of energy.  In plain language, this doctrine teaches that every change in every part of the physical world, every motion in matter, must be preceded by physical conditions which may be regarded as the equivalent of the change in question.

But this makes the physical world a closed system, a something complete in itself.  Where is there room in such a system for minds?