no man of any school has the right to deny. The
only legitimate question is: _What is the nature_ of the relation? Is
it _causal_, or should it be conceived to be _something else_?

The whole matter will be more fully discussed in Chapter XI. This
chapter I shall close with a brief summary of the points which the
reader will do well to bear in mind when he occupies himself with
parallelism.

(1) Parallelism is a protest against the interactionist's tendency to
materialize the mind.

(2) The name is a figurative expression, and must not be taken
literally. The true relation between mental phenomena and physical is
given in certain common experiences that have been indicated, and it is
a unique relation.

(3) It is a fixed and absolutely dependable relation. It is impossible
that there should be a particular mental fact without its corresponding
physical fact; and it is impossible that this physical fact should
occur without its corresponding mental fact.

(4) The parallelist objects to calling this relation _causal_, because
this obscures the distinction between it and the relation between facts
both of which are physical. He prefers the word "concomitance."

(5) Such objections to parallelism as that cited above assume that the
concomitance of which the parallelist speaks is analogous to physical
concomitance. The chemist puts together a volume of hydrogen gas and a
volume of chlorine gas, and the result is two volumes of hydrochloric
acid gas. We regard it as essential to the result that there should be
the two gases and that they should be brought together. But the fact
that the chemist has red hair we rightly look upon as a concomitant
phenomenon of no importance. The result would be the same if he had
black hair or were bald. But this is not the concomitance that
interests the parallelist. The two sorts of concomitance are alike
only in the one point. Some phenomenon is regarded as excluded from
the series of causes and effects under discussion. On the other hand,
the difference between the two is all-important; in the one case, the
concomitant phenomenon is an accidental circumstance that might just as
well be absent; in the other, it is nothing of the sort; it _cannot_ be
absent--the mental fact _must_ exist if the brain-change in question
exists.

It is quite possible that, on reading this list of points, one may be
inclined to make two protests.

First: Is a parallelism so carefully guard