we could never possess knowledge of any kind. The senses
thus hold the keys which unlock the doors of intelligence to
the mind, and the senses are physical, not mental, things.
Apparently, therefore, the most simple and fundamental
operations of consciousness are bound up with the existence
and activity of certain bodily organs.

Common observation also informs us (2) that the expres-
sions of mind ordinarily take the form of muscular move-
ments which we call acts. We hear a bell and our conscious-
ness of the sound results in our going to open the door. We
consider a course of action, and the outcome of our delibera-
tion issues in the form of words or deeds, all of which con-
sist primarily in muscular movements. Strange as it may
appear, even keeping still involves muscular activity. It
would accordingly seem as though the mind were hemmed in
between the sense organs on the one hand and the muscles
on the other. It would be a truer expression of the facts,
however, to say that these are the tools with which the mind
works. Through the sense organs it receives its raw material,
and by its own operations this material is worked up and
organised into the coherent product which we call intelli-
gence. This intelligence is then made effective in practical
ways through the rationally controlled action of the voluntary
muscles.

There are other facts of a well-known kind whose precise
purport is, perhaps, less evident, but whose general implica-
tion of intimate connections between mind and body is iden-
tical with that of the considerations which we have just
mentioned. We know, for example, that blows and wounds
may seriously disturb consciousness, or even destroy it. The
similar effects of many drugs, such as alcohol, ether, and
hashish, are matters of common knowledge. Even coffee
and tea exercise a mild influence upon our psychical mood,
and the change in general disposition which frequently fol-
lows indulgence in a satisfactory meal is a phenomenon

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