loped or gained it by experience or observation. And
all the members of the species have inherited it in much the same
degree of perfection.

Concerning the origin of instincts there are several theories. Some
instincts would seem to be the result of non-intelligent, perhaps
unconscious, habits becoming fixed by heredity and improved by
natural selection; others would appear to be modifications of
actions originally due to intelligence. Instinct is therefore
characterized by consciousness of the stimulus to act, of the means
and end, without the knowledge of the exact adaptation of means to
end. It is hereditary and characterizes species or large groups.

3. Intelligent Action. You come in cold and sit down before an open
fire. You push the brands together to make the fire burn. Applying
once more the criterion of consciousness to this action we notice
that you are conscious of the stimulus to act, of the steps of the
action, and of the end to be attained, exactly as in instinctive
action. But finally, and this is the essential characteristic of
intelligent action, you are aware to a certain extent of the fitness
of the means to the attainment of the end. This piece of knowledge
you had to acquire for yourself. Erasmus Darwin defined a fool as a
man who had never tried an experiment. Experience and observation,
not heredity, are the sources of intelligence. Intelligence is power
to think, and a man may be very learned--for do we not have learned
pigs?--and yet have very little real intelligence. Hence this is
possessed by different individuals in very varying degrees.

We may now briefly compare these three kinds of nervous action.

Reflex action is involuntary and unconscious. The actor may, and
usually does, become conscious of the action after it has been
commenced or completed, but this is not at all necessary or
universal.

Instinctive action is to a certain extent voluntary and conscious.
The actor is conscious of the stimulus, the means and mode, and the
end or purpose of the action. Of the exact fitness or adaptation of
the means to the end the actor is unconscious.

Intelligent action is conscious and voluntary. The actor is
conscious of the stimulus to act, of the means and mode, and to a
certain extent of the adaptation of the means to the end. This last
item of knowledge, lacking in instinctive action, is acquired by
experience or observation.

Reflex action may be regarded as a comparatively mechan