to psychology to learn about the nature of children and to find out how
we can influence them. Psychology is therefore the basis of the science
of education.

Since different kinds of work demand, in some cases, different kinds of
ability, the psychology of individual differences can be of service in
selecting people for special kinds of work. That is to say, we must have
sometime, if we do not now, a psychology of professions and vocations.
Psychological investigations of the reliability of human evidence make
the science of service in the court room. The study of the laws of
attention and interest give us the psychology of advertising. The study
of suggestion and abnormal states make psychology of use in medicine. It
may be said, therefore, that psychology, once abstract and unrelated to
any practical interests, will become the most useful of all sciences, as
it works out its problems and finds the laws of human behavior.

At present, the greatest service of psychology is to education. So true
is this that a department has grown up called "educational psychology,"
which constitutes at the present time the most important subdivision of
psychology. While in this book we treat briefly of the various
applications of psychology, we shall have in mind chiefly its
application to education.

=The Science of Education.= Owing to the importance which psychology has
in the science of education, it will be well for us to make some inquiry
into the nature of education. If the growth, development, and learning
of children are all controlled and determined by definite causal
factors, then a systematic statement of all these factors would
constitute the science of education. In order to see clearly whether
there is such a science, or whether there can be, let us inquire more