Thus we might expect that it would be a vain task to seek anywhere in nature for evidence of Divine action, such that no one could sanely deny it. God will not allow Himself to be caught at the bottom of any man's crucible, or yield Himself to the experiments of gross-minded and irreverent inquirers. The natural, like the supernatural, revelation appeals to _the whole_ of man's mental nature and not to the _reason alone_.[287] None, therefore, need feel disappointed that evidence of the direct action of the first cause in merely natural phenomena ever eludes our grasp; for assuredly those same phenomena will ever remain fundamentally inexplicable by physical science alone. There being then nothing in either authority or reason which makes "evolution" repugnant to Christianity, is there anything in the Christian doctrine of "Creation" which is repugnant to the theory of "evolution"? Enough has been said as to the distinction between absolute and derivative "creation." It remains to consider the successive "evolution" (Darwinian and other) of "specific forms," in a theological light. As to what "evolution" is, we cannot of course hope to explain it completely, but it may be enough to define it as the manifestation to the intellect, by means of sensible impressions, of some ideal entity (power, principle, nature, or activity) which before that manifestation was in{271} a latent, unrealized, and merely "potential" state--a state that is capable of becoming realized, actual, or manifest, the requisite conditions being supplied. "Specific forms," kinds or species, are (as was said in the introductory chapter) "peculiar congeries of characters or attributes, innate powers and qualities, and a certain nature realized in individuals." Thus, then, the "evolution of specific forms" means the actual manifestation of special powers, or natures, which before were latent, in such a successive manner that there is in some way a genetic relation between posterior manifestations and those which preceded them. On the special Darwinian hypothesis the manifestation of these forms is determined simply by the survival of the fittest of many indefinite variations. On the hypothesis here advocated the manifestation is controlled and helped by such survival, but depends on some unknown internal law or laws which determine variation at special times and in special directions. Professor Agassiz objects to the evolution theory, on the ground that "species, genera, families, &c., exist as thoughts, individuals as facts,"[288] and he offers the dilemma, "If species do not exist at all, as the supporters of the transmutation theory maintain, how can they vary? and if individuals alone exist, how can the differences which may be observed among them prove the variability of species?"