distance, and try to judge it as he would judge a type of doctrine
presented to him for the first rime. And in the accomplishment of this
task he can find no greater aid than the study of the history of
philosophy.

It is at first something of a shock to a man to discover that
assumptions which he has been accustomed to make without question have
been frankly repudiated by men quite as clever as he, and, perhaps,
more critical. It opens the eyes to see that his standards of worth
have been weighed by others and have been found wanting. It may well
incline him to reexamine reasonings in which he has detected no flaw,
when he finds that acute minds have tried them before, and have
declared them faulty.

Nor can it be without its influence upon his judgment of the
significance of a doctrine, when it becomes plain to him that this
significance can scarcely be fully comprehended until the history of
the doctrine is known. For example, he thinks of the mind as somehow
in the body, as interacting with it, as a substance, and as immaterial.
In the course of his reading it begins to dawn upon his consciousness
that he has not thought all this out for himself; he has taken these
notions from others, who in turn have had them from their predecessors.
He begins to realize that he is not resting upon evidence independently
found in his own experience, but has upon his hands a sheaf of opinions
which are the echoes of old philosophies, and whose rise and
development can be traced over the stretch of the centuries. Can he
help asking himself, when he sees this, whether the opinions in
question express the truth and the whole truth? Is he not forced to
take the critical attitude toward them?