interpretation put upon it by our previous experience. "Many a weak,
obscure, and fleeting perception would pass almost unnoticed into
obscurity, did not the additional activity of apperception hold it fast
in consciousness. This sharpens the senses, _i.e._, it gives to the
organs of sense a greater degree of energy, so that the watching eye
now sees, and the listening ear now hears, that which ordinarily would
pass unnoticed. The events of apperception give to the senses a
peculiar keenness, which underlies the skill of the money-changer in
detecting a counterfeit among a thousand bank-notes, notwithstanding
its deceptive similarity; of the jeweler who marks the slightest,
apparently imperceptible, flaw in an ornament; of the physicist who
perceives distinctly the overtones of a vibrating string. According to
this we see and hear not only with the eye and ear, but quite as much
with the help of our present knowledge, with the apperceiving content
of the mind." (Apperception, Lange, De Garmo, p. 21.)

Some even intelligent and sensible people can walk through Westminster
Abbey and see nothing but a curious old church with a few graves and
monuments. To a person well-versed in English history and literature
it is a shrine of poets, a temple of heroes, the common resting-place
of statesmen and kings.

Secondly, what is the _effect on the old ideas_? Every idea that newly
enters the mind produces changes in the older groups and series of
thought. Any one new idea may cause but slight changes, but the
constant influx of new experiences works steadily at a modification and
rearrangement of our previous stores of thought. Faulty and incomplete
groups and concepts are corrected or enlarged; that is, changed from
psychical into logical notions. Children are surprised to find little
flowers on the oaks, maples, walnuts, and other large forest trees. On
account of the small size of the blossoms, heretofore unnoticed, they
had not thought of the great trees as belonging to the flowering
plants. Their notion of flowering plants is, therefore, greatly
enlarged by a few new observations. The bats flying about in the
twilight have been regarded as birds; but a closer inspection shows
that they belong to another class, and the notion bird must be limited.
As already observed in the discussion of induction, most of our
psychical notions are thus faulty and incomplete; _e.g._, the ideas
fruit, fish, star, insect, mineral,