roundness, the firmness, the fragrance, and the taste of the apple are
not present to Sense, but are made present to Consciousness by the act
of Perception. The eye sees a certain coloured surface; the mind sees
at the same instant many other co-existent but unapparent facts--it
reinstates in their due order these unapparent facts. Were it not for
this mental vision supplying the deficiencies of ocular vision, the
coloured surface would be an enigma. But the suggestion of Sense
rapidly recalls the experiences previously associated with the object.
The apparent facts disclose the facts that are unapparent.

Inference is only a higher form of the same process. We look from the
window, see the dripping leaves and the wet ground, and infer that rain
has fallen. It is on inferences of this kind that all knowledge
depends. The extension of the known to the unknown, of the apparent to
the unapparent, gives us Science. Except in the grandeur of its sweep,
the mind pursues the same course in the interpretation of geological
facts as in the interpretation of the ordinary incidents of daily
experience. To read the pages of the great Stone Book, and to perceive
from the wet streets that rain has recently fallen, are forms of the
same intellectual process. In the one case the inference traverses
immeasurable spaces of time, connecting the apparent facts with causes
(unapparent facts) similar to those which have been associated in
experience with such results; in the other case the inference connects
wet streets and swollen gutters with causes which have been associated
in experience with such results. Let the inference span with its mighty
arch a myriad of years, or link together the events of a few minutes,
in each case the arch rises from the ground of familiar facts, and
reaches an antecedent which is known to be a cause capable of producing
them.