Derivative laws, not causative, may certainly be extended beyond the limits of observation, but only to cases _adjacent_ in time. Thus, we may not predict that the sun will rise this day 20,000 years, but we can predict that it will rise to-morrow, on the ground that it has risen every day for the last 5,000 years. The latter prediction is lawful, _because_, while we know the causes on which its rising depends, we know, also, that there has existed hitherto no perceptible cause to counteract them; and that it is opposed to experience that a cause imperceptible for 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 primæval 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.