be furnished by the actor or by his own intelligence.
A second principle of the method will be by a study of the whole range of animal life, and especially of forms whose conduct presents obvious resemblances to that of man, to discover what instinctive impulses may be expected to operate in him.
A third principle will be to search for criteria, whereby instinctive impulses or their derivatives arising in the mind can be distinguished from rational motives, or at any rate motives in which the instinctive factor is minimal. Thus will be furnished for the method the objective standard for the judgment of mental observations which is the one indispensable requirement in all psychological inquiries.
When it is known what types of instinctive mechanisms are to be expected, and under what aspects they will appear in the mind, it is possible to press inquiry into many of the obscurer regions of human behaviour and thought, and to arrive at conclusions which, while they are in harmony with the general body of biological science, have the additional value