llions of men. And again only
the higher layer of the neurons in the population sees its doings
recorded in the annals of history; and yet whatever those leaders of
action and thought and emotion may achieve is dependent upon and working
on the actions of those millions of subcortical population neurons. The
historical record has its unity through the interrelation of all parts
of historical mankind.

But after all the psychologist has no less a right to speak of freedom.
Of course his freedom cannot mean exemption from causality. Whatever
happens in the psychological system must be perfectly determined by the
foregoing causes. But the psychologist has good reason to discriminate
between those actions which result from the normal psychophysical
factors and such actions as result from broken machinery. If the brain
is poisoned by alcohol or in fever, if an infectious disease has
destroyed the brain cells, action is no longer the outcome of the
normal cooeperation of the organs, and even those clusters of neural
activities which are accompanied by the consciousness of the own
personality lose their control of the motor outcome. The man in delirium
or paralysis acts without causal connection with his past; the action
is, therefore, not the product of his whole personality, and the
psychologist is justified in calling the man unfree. But, whenever the
motor response results from the undisturbed cooeperation of the normal
brain parts, then the inherited equipment and the whole experience and
the whole training, the acquired habits and the acquired inhibitions
will count in bringing about the reaction. This is the psychological
freedom of man. The unity of an interconnected composite and the freedom
of causal determination through normal cooeperation of all its parts
characterize the only personality which the psychologist has to
recognize.

IV

PSYCHOLOGY AND MEDICINE

We are now ready to take the first step towards an examination of the
problem of curing suffering mankind. So far we have spoken only of the
meaning of psychology, of its principles and of its fundamental theories
as to mind and brain. We have moved in an entirely theoretical sphere.
Now we approach a field in which everything is controlled by a practical
aim, the treatment of the sick. Yet our discussion of psychology should
have brought us much nearer to the point where we can enter this realm
of medicine. Everything depends on the right point o