These latter always possess position and extension, i. e., they
occupy space. Psychical facts, or events, never do; on the
other hand they possess one characteristic which, so far as
we know, is wholly wanting to physical facts, in that they
exist for themselves. A man not only has sensations and
ideas, he knows that he has them. A stone or other physical
object has no such knowledge of its own existence or of its
own experiences. Yet, whatever may be the value of these
distinctions, we need entertain no real fear of encountering
any serious misapprehension of the inner nature of conscious-
ness, for each one of us experiences it every day for himself
and each is thus fitted to discuss it with some measure of
accuracy.

Former Definitions of Psychology. -- Formerly psychology
was often defined as the science of the soul. But the word
soul generally implies something above and beyond the
thoughts and feelings of which we are immediately conscious;
and as it is these latter phenomena with which psychology is
primarily engaged, this definition is now rarely used by care-
ful writers. Psychology is also defined at times as the
science of mind. The objection to this definition is that the
word mind ordinarily implies a certain continuity, unity, and
personality, which is, indeed, characteristic of normal human
beings; but which may, for all we can see, be wholly lacking
in certain unusual psychical experiences like those of in-
sanity, or those of dream states, and may be wanting at times
in animals. All consciousness everywhere, normal or abnor-
mal, human or animal, is the subject matter which the
psychologist attempts to describe and explain; and no defini-
tion of his science is wholly acceptable which designates more
or less than just this. Nevertheless, we shall often employ
the term mind in this book, using it to designate the entirety
of the intelligent processes which occur in the organism.

The Procedure of the Psychologist. -- In his description of
conscious processes the psychologist attempts to point out the

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