This view of evolution is not saved by the theory that behind these chemical affinities and physical relations there is an unknowable power of which they are but the manifestations: for the power is not unknowable if its manifestations are limited to these known manifestations; and if they are not so limited, but operate in other ways with new factors, not comprised in our estimate of them, then our explanatory system is at fault, and has to be abandoned or amended. The recognition of an unknowable power behind chemistry and physics, yet limited by the laws of chemistry and physics, is equal only to our estimate of chemistry and physics. We could but address it as Oh my Lord Chemistry! Oh my Lord Physics! But we have shown in our previous criticisms that this view of evolution, as dealing with purely physical factors, is inadequate to explain the cosmical histories. We have criticised adversely Mr. Spencer's attempts so to explain biological development; and we have indicated the necessity for supposing that other superior factors are present in biological evolution. We do not know that Mr. Spencer disputes it--his work is too vague and inconsistent to enable us to say precisely what he does and what he does not teach. But the admission of additional factors does not destroy the theory of evolution. Darwin and Spencer and the modern school have established, beyond dispute, the fact of orderly development in the cosmos. We are forced, therefore, to admit both evolution and the presence in it, so far as Biology is concerned, and probably also as regards all the changes anterior to the beginnings of life, of a factor over and above the chemical and physical factors. The nature of this factor we do not know, nor do we know how, as having an orderly relation to chemical and physical events, its law is to be expressed in such a manner as to enable us to understand how organisms arose and were developed. Here, indeed, we can recognise a power, and an inscrutable one: but inasmuch as it is inscrutable it spoils our philosophy--our systems of explanations--and laughs at our formulas. But after all, if we succeed in establishing purposive actions as incidents in a process of equilibration, what have we gained? We have gained a scientific explanation of all purposive actions as well as of all actions of organisms in general. They all stand upon the same footing--that is to say they are all equally explicable as parts of the universal process. They are all equally equilibrations, and so justified in their order of occurrence. They rank alike as incidents in a line of causation explicable by the law of equilibration.