228 THE FACTORS OF THE MIND

unless some degree of causal determination" is presupposed,
his anticipations can have no basis. The philosophical
thinker searches rather for explanatory realities behind the
immediate facts. In dealing with mental phenomena, we
are all of us tempted to philosophize. But when the prac-
tical man begins to do so, particularly if (as with the medical
worker) his practical training has left him unaware of the
pitfalls that await the amateur philosopher, he is prone to
carry over his practical concepts into the realm of meta-
physics, regardless of the fallacies that such a procedure
entails. An austerely scientific attitude comes last of all.
The scientist is, or should be, the most cautious of thinkers.
His concern is solely with the systematic description of his
own restricted province. The co-ordination of his facts will
necessitate inference : but his inferences must rest as much
as possible on the facts themselves and as little as possible
upon assumptions. His method, therefore, will be, not to
guess at supposed realities to satisfy some practical or philo-
sophical need, but ruthlessly at every step to eliminate
whatever is neither proved nor requisite for proof. Let us
remember, then, that a type of explanation that may be
temporarily helpful on the lowly level of applied or practical
psychology may be both a snare and a delusion on the higher
level of metaphysical speculation, and can only be accepted
on the intermediate level of pure or empirical psychology
if it has stood the sternest scrutiny.

(a) On the Level of Applied Psychology.—In practical
psychology, as distinct from theoretical, there is some excuse
for causal language. In the field of educational, vocational,
and clinical work, the logical grounds that the psychologist
seeks are grounds for inferences specifically in regard to the
future. Now a cause, at any rate in the popular mind, always
precedes its effect in time. If, therefore, we postulate a
law of causation, and search for these anterior causes, we
may be able to deduce what will occur in the future from
conditions that are ascertainable now. Instead, then, of a
symmetrical or reciprocal dependence, such as could be
expressed by an abstract function, the practical man is
interested only in the asymmetrical or one-sided dependence
of the future on the present or the past; and this one-sided