ABSTRACT
I T is possible, by employing various combinations and per-mutations, to derive a surprisingly large number of deduc-tions from a few primary principles. Some of these are inevitably trivial; in other cases the conclusion arrived at after an involved sequence of logical operations turns out to be a proposition which no reasonable person would think of disputing, a commonsense fact. It is natural that the clinician, conscious of the urgency of the problems which confront him, should sometimes be a little impatient of an activity which yields no immediate addition to his techniques. Yet we must not lose sight of the fact that-even from the strictly practical point of view-systematic scrutiny of the logical consequences of a theory is very necessary, not only in order to identify new problems which may be fruitfully investigated, but also as a means of testing the principles themselves.
