In studying this subject we must remember certain things:

(_a_) That telepathy is a highly complex phenomenon, and for that reason
we must not expect to find its solution easily or state it in a single
sentence.

(_b_) That we must consider it from the double standpoint, physical and
mental; and

(_c_) That we must consider the conditions affecting the operator, the
subject, and, if possible, the connection between them.

All scientific explanation consists in reducing the unknown to terms of
the known. We can often _classify_ a phenomenon without being able to
_explain_ its innermost nature. If we discover its laws, we have
advanced to that extent.

Dr. J. Ochorowicz, who has made a prolonged and minute study of this
question, writes as follows regarding the necessary conditions to be
observed in the operator:

"On the side of the _operator_ the conditions have been very little
studied. But it is probable:

"1. That there are personal differences.

"2. That these differences may be due not only to the degree of
thought intensity, but also to the nature of the thought itself,
according as it is visual, auditive, or motor.

"3. That some account has to be taken of a sort of accord, of
concordance between the two intelligences.

"4. That excessive will-power impairs the definiteness of the
transmission without much enhancing its intensity.

"5. That strong, persistent, prolonged thinking of a thought
repeated for a longer or shorter time constitutes a condition in
the highest degree favourable.

"6. That any distraction which causes the thought to disappear for
a moment, or that makes it cease to be isolated, seems eminently
unfavourable to the mental action.

"7. That, nevertheless, thoughts that are not intense, and even
thoughts that are at the moment unconscious (subconscious), may be
transmitted involuntarily.

"8. That the muscular efforts which usually accompany an exertion
of will are more or less indifferent; but that the muscle
expression of the operator may be useful, subjectively, by reason
of the habitude that connects thought with these expressional
signs.

"It follows from these considerations that the operator should
insist less upon the 'I will it' than upon the content of that
willing; and hence it is probable that, properly speaking, it is
not t