xposition. If, however, the aim is not merely to cause the
reader to understand the proposition, but also to believe that it is true,
we have argument. In either case we have a paragraph developed by specific
instances as discussed in Section 44. Notice how in the following
paragraph the author brings forward specific cases in order to prove the
proposition:--

Nearly everything that an animal does is the result of an inborn instinct
acted upon by an outward stimulus. The margin wherein intelligent choice
plays a part is very small.... 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 of 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 it. 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
afterthought that an animal is not capable of. A horse will hesitate to go
upon thin ice or frail bridges. This, no doubt, is an inherited instinct
which has arisen in its ancestors from their fund of general experience
with the world. How much with them has depended upon a secure footing! A
pair of house-wrens had a nest in my well-curb; when the young were partly
grown and heard any one enter the curb, they would set up a clamorous
calling for food. When I scratched against the sides of the curb beneath
them like some animal trying to climb up, their voices instantly hushed;
the i