ology, and in morals as
compared with physics. Nevertheless, the fact that these various
sciences are all human, and that here, for instance, we are able to
mention them in one breath and to compare their natures, is proof that
their spheres touch somehow, even if only peripherally. Since common
knowledge, which knows of them all, is itself an incipient science, we
may be sure that some continuity and some congruity obtains between
their provinces. Some aspect of each must coincide with some aspect of
some other, else nobody who pursued any one science would so much as
suspect the existence of the rest. Great as may be the aversion of
learned men to one another, and comprehensive as may be their ignorance,
they are not positively compelled to live in solitary confinement, and
the key of their prison cells is at least in their own pocket.

[Sidenote: Two chief kinds of science, physics and dialectic.]

Some sciences, like chemistry and biology, or biology and anthropology,
are parted only, we presume, by accidental gaps in human knowledge; a
more minute and better directed study of these fields would doubtless
disclose their continuity with the fields adjoining. But there is one
general division in science which cuts almost to the roots of human
experience. Human understanding has used from the beginning a double
method of surveying and arresting ideally the irreparable flux of being.
One expedient has been to notice and identify similarities of character,
recurrent types, in the phenomena that pass before it or in its own
operations; the other expedient has been to note and combine in one
complex object characters which occur and reappear together. The latter
feat which is made easy by the fact that when various senses are
stimulated at once the inward instinctive reaction--which is felt by a
primitive mind more powerfully than any external image--is one and not
consciously divisible.

The first expedient imposes on the flux what we call ideas, which are
concretions in discourse, terms employed in thought and language. The
second expedient separates the same flux into what we call things, which
are concretions in existence, complexes of qualities subsisting in space
and time, having definable dynamic relations there and a traceable
history. Carrying out this primitive diversity in reflection science
has moved in two different directions. By refining concretions in
discourse it has attained to mathematics, logic, and t