least within the portion of the universe within our
observation, and adjacent cases, but must prove the law to be either
true or false. It has, in fact, never been found to be false, but in
ever increasing multitudes of cases to be true; and phenomena, even
when, from their rarity or inaccessibility, or the number of modifying
causes, they are not reducible _universally_ to any law, yet _in some
instances_ do conform to this. Thus, it may be regarded as coextensive
with all human experience, at which point the distinction between
empirical laws and laws of nature vanishes. Formerly, indeed, it was
only a very high probability; but, with our modern experience, it is,
practically, absolutely certain, and it confirms the particular laws of
causation, whence itself was drawn, when there seem to be exceptions to
them. All narrower inductions got by simple enumeration are unsafe,
till, by the application to them of the four methods, the supposition of
their falsity is shown to contradict _this_ law, though it was itself
arrived at by simple enumeration.

CHAPTER XXII.

UNIFORMITIES OF COEXISTENCE NOT DEPENDENT ON CAUSATION.

Besides uniformities of succession, which always depend on causation,
there are uniformities of coexistence. These also, whenever the
coexisting phenomena are effects of causes, whether of one common cause
or of several different causes, depend on the laws of their cause or
causes; and, till resolved into these laws, are mere empirical laws. But
there are some uniformities of coexistence, viz. those between the
ultimate properties of _kinds_, which do not depend on causation, and
therefore seem entitled to be classed as a peculiar sort of laws of
nature. As, however, the presumption always is (except in the case of
those _kinds_ which are called _simple substances_ or elementary natural
agents), that a thing's properties really depend on causes though not
traced, and we _never_ can be certain that they do not; we cannot safely
claim (though it _may_ be an ultimate truth) higher certainty than that
of an empirical law for any generalisation about coexistence, that is to
say (since _kinds_ are known to us only by their properties, and,
consequently, all assertions about them are assertions about the
coexistence of something with those properties), about the properties of
_kinds_.

Besides, no rigorous inductive system can be applied to the uniformities
of coexistence, since there is no general