anity, Dr. Hart says:

* Cambridge, 1912; 2nd edition, 1914. The following
references are to the second edition.

"The psychological conception [of insanity] is based on the view that
mental processes can be directly studied without any reference to the
accompanying changes which are presumed to take place in the brain, and
that insanity may therefore be properly attacked from the standpoint of
psychology"(p. 9).

This illustrates a point which I am anxious to make clear from the
outset. Any attempt to classify modern views, such as I propose to
advocate, from the old standpoint of materialism and idealism, is only
misleading. In certain respects, the views which I shall be setting
forth approximate to materialism; in certain others, they approximate to
its opposite. On this question of the study of delusions, the practical
effect of the modern theories, as Dr. Hart points out, is emancipation
from the materialist method. On the other hand, as he also points
out (pp. 38-9), imbecility and dementia still have to be considered
physiologically, as caused by defects in the brain. There is no
inconsistency in this If, as we maintain, mind and matter are neither of
them the actual stuff of reality, but different convenient groupings of
an underlying material, then, clearly, the question whether, in regard
to a given phenomenon, we are to seek a physical or a mental cause, is
merely one to be decided by trial. Metaphysicians have argued endlessly
as to the interaction of mind and matter. The followers of Descartes
held that mind and matter are so different as to make any action of the
one on the other impossible. When I will to move my arm, they said,
it is not my will that operates on my arm, but God, who, by His
omnipotence, moves my arm whenever I want it moved. The modern doctrine
of psychophysical parallelism is not appreciably different from this
theory of the Cartesian school. Psycho-physical parallelism is the
theory that mental and physical events each have causes in their own
sphere, but run on side by side owing to the fact that every state of
the brain coexists with a definite state of the mind, and vice versa.
This view of the reciprocal causal independence of mind and matter has
no basis except in metaphysical theory.* For us, there is no necessity
to make any such assumption, which is very difficult to harmonize with
obvious facts. I receive a letter inviting me to dinner: the letter is
a physical f