l, or a
Chinaman in the street, calls for explanation; and among some nations,
eclipses have been explained by supposing a dragon to devour the sun or
moon; solitary boulders, as the missiles of a giant; and so on. Such
explanations, plainly, are attempts to regard rare phenomena as similar
to others that are better known; a snake having been seen to swallow a
rabbit, a bigger one may swallow the sun: a giant is supposed to bear
much the same relation to a boulder as a boy does to half a brick. When
any very common thing seems to need no explanation, it is because the
several instances of its occurrence are a sufficient basis of
assimilation to satisfy most of us. Still, if a reason for such a thing
be demanded, the commonest answer has the same implication, namely, that
assimilation or classification is a sufficient reason for it. Thus, if
climbing trees is referred to the need of exercise, it is assimilated to
running, rowing, etc.; if the customs of a savage tribe are referred
to the command of its gods, they are assimilated to those things that
are done at the command of chieftains.

Explanation, then, is a kind of classification; it is the finding of
resemblance between the phenomenon in question and other phenomena. In
Mathematics, the explanation of a theorem is the same as its proof, and
consists in showing that it repeats, under different conditions, the
definitions and axioms already assumed and the theorems already
demonstrated. In Logic, the major premise of every syllogism is an
explanation of the conclusion; for the minor premise asserts that the
conclusion is an example of the major premise.

In Concrete Sciences, to discover the cause of a phenomenon, or to
derive an empirical law from laws of causation, is to explain it;
because a cause is an invariable antecedent, and therefore reminds us
of, or enables us to conceive, an indefinite number of cases similar to
the present one wherever the cause exists. It classifies the present
case with other instances of causation, or brings it under the universal
law; and, as we have seen that the discovery of the laws of nature is
essentially the discovery of causes, the discovery and derivation of
laws is scientific explanation.

The discovery of quantitative laws is especially satisfactory, because
it not only explains why an event happens at all, but why it happens
just in this direction, degree, or amount; and not only is the given
relation of cause and effec