tempts to deny the existence of any relation between
mind and body. Parallelism in its leading forms we
studied in considerable detail and, I think, in no un-
sympathetic spirit; and I see no conceivable reason
for altering the unfavorable judgment to which we
were forced. Materialism also we analyzed with
some care; and the great difficulties which it involved
were so patent that I feel sure nothing would be
gained by a reconsideration of its assertions. Of all
the proposed solutions of our problem Interaction
alone was put aside with a rather summary and in-
adequate consideration. We hardly more than
glanced at it, as you will remember, and not yet real-
izing how difficult was our problem, we hurried on
to more promising suggestions. Having seen now,
through a slow and I fear painful course of reason-
ing, how fallacious were all these promises, we owe
it in fairness to ourselves to give to Interaction the
same sort of serious consideration that we have given
to each of the other hypotheses.

What then, we must ask ourselves, were the dif-
ficulties which we found with Interaction which
made us pass it by as unsatisfactory? One of them
which indeed we hardly made explicit at the time
but which undoubtedly influenced our judgment con-

-132-