r so long should start into immensity in a day. If the
uniformity is empirical only, that is, if we do not know the causes, and
if we infer that they remain uncounteracted from their effects alone, we
still can extend the law to adjacent cases, but only to cases still more
closely adjacent in time; since we can know neither whether changes in
these unknown causes may not have occurred, nor whether there may not
exist now an adverse cause capable after a time of counteracting them.

An empirical law cannot generally be extended, in reference to _Place_,
even to adjacent cases (since there is no uniformity in the collocations
of primaeval causes). Such an extension is lawful only if the new cases
are _presumably_ within the influence of the same individual causes,
even though unknown. When, however, the causes are known, and the
conjunction of the effects is deducible from laws of the causes, the
derivative uniformity may be extended over a wider space, and with less
abatement for the chance of counteracting causes.

CHAPTER XX.

ANALOGY.

One of the many meanings of _Analogy_ is, Resemblance of Relations. The
value of an analogical argument in this sense depends on the showing
that, on the common circumstance which is the _fundamentum relationis_,
the rest of the circumstances of the case depend. But, generally, _to
argue from analogy_ signifies to infer from resemblance in some points
(not necessarily in _relations_) resemblance in others. Induction does
the same: but analogy differs from induction in not requiring the
previous proof, by comparison of instances, of the invariable
conjunction between the known and the unknown properties; though it
requires that the latter should not have been ascertained to be
_unconnected_ with the common properties.

If a fair proportion of the properties of the two cases are known, every
resemblance affords ground for expecting an indefinite number of other
resemblances, among which the property in question may perhaps be found.
On the other hand, every dissimilarity will lead us to expect that the
two cases differ in an indefinite number of properties, including,
perhaps, the one in question. These dissimilarities may even be such as
would, in regard to one of the two cases, imply the absence of that
property; and then every resemblance, as showing that the two cases have
a similar nature, is even a reason for presuming against the presence of
that property. Hence, the v