§ 40. But it will be aided by another. From the evidence above set forth, it may be inferred that a secondary influence will by and by enforce this primary one. That law is universal, will become an irresistible conclusion when it is perceived that _the progress in the discovery of laws itself conforms to law_; and when it is hence understood why certain groups of phenomena have been reduced to law, while other groups are still unreduced. When it is seen that the order in which uniformities are recognized, must depend upon the frequency and vividness with which they are repeated in conscious experience; when it is seen that, as a matter of fact, the most common, important, conspicuous, concrete and simple uniformities were the earliest recognized, because they were experienced oftenest and most distinctly; when it is further seen that from the beginning the advance has been to the recognition of uniformities which, from one or other circumstance, were less often experienced; it will by implication be seen that long after the great mass of phenomena have been generalized, there must remain phenomena which, from their rareness, or unobtrusiveness, or seeming unimportance, or complexity, or abstractness, are still ungeneralized. Thus will be furnished a solution to a difficulty sometimes raised. When it is asked why the universality of law is not already fully established, there will be the answer that the directions in which it is not yet established are those in which its establishment must necessarily be latest. That state of things which is inferable beforehand, is just the state which we find to exist. If such coexistences and sequences as those of Biology and Sociology are not yet reduced to law, the presumption is not that they are irreducible to law, but that their laws elude our present means of analysis. Having long ago proved uniformity throughout all the lower classes of relations; and having been step by step proving uniformity throughout classes of relations successively higher and higher; if we have not at present succeeded with the highest classes, it may be fairly concluded that our powers are at fault, rather than that the uniformity does not exist. And unless we make the absurd assumption that the process of generalization, now going on with unexampled rapidity, has reached its limit, and will suddenly cease, we must infer that ultimately mankind will discover a constant order of manifestation even in the most involved, obscure, and abstract phenomena. * * * * * § 41. Not even yet, however, have we exhausted the evidence. The foregoing arguments have to be merged in another, still more cogent, which fuses all fragmentary proofs into one general proof.