eeping up the
litter. The birds could not effect an entrance into the interior of
the plate, but they could thrust in their nesting-material, and so
they persisted week after week, stimulated by the presence of a cavity
beyond their reach. The case is a good illustration of the blind
working of instinct.

Animals have keen perceptions,--keener in many respects than our
own,--but they form no conceptions, have no powers of comparing one
thing with another. They live entirely in and through their senses.

It is as if the psychic world were divided into two planes, one above
the other,--the plane of sense and the plane of spirit. In the plane
of sense live the lower animals, only now and then just breaking for a
moment into the higher plane. In the world of sense man is immersed
also--this is his start and foundation; but he rises into the plane of
spirit, and here lives his proper life. He is emancipated from sense
in a way that beasts are not.

Thus, I think, the line between animal and human psychology may be
pretty clearly drawn. It is not a dead-level line. Instinct is
undoubtedly often modified by intelligence, and intelligence is as
often guided or prompted by instinct, but one need not hesitate long
as to which side of the line any given act of man or beast belongs.
When the fox resorts to various tricks to outwit and delay the hound
(if he ever consciously does so), he exercises a kind of
intelligence,--the lower form which we call cunning,--and he is
prompted to this by an instinct of self-preservation. When the birds
set up a hue and cry about a hawk or an owl, or boldly attack him,
they show intelligence in its simpler form, the intelligence that
recognizes its enemies, prompted again by the instinct of
self-preservation. When a hawk does not know a man on horseback from a
horse, it shows a want of intelligence. When a crow is kept away from
a corn-field by a string stretched around it, the fact shows how
masterful is its fear and how shallow its wit. When a cat or a dog,
or a horse or a cow, learns to open a gate or a door, it shows a
degree of intelligence--power to imitate, to profit by experience. A
machine could not learn to do this. If the animal were to close the
door or gate behind it, that would be another step in intelligence.
But its direct wants have no relation to the closing of the door, only
to the opening of it. To close the door involves an after-thought that
an animal is not capable of. A