Properly speaking, then, the religious theory of final causes does not explain any of the phenomena of Nature:  it merely re-states the phenomena as observed—­or, if we prefer so to say, it is itself an ultimate and universal explanation of all possible phenomena taken collectively.  For it must be admitted that behind all possible explanations of a scientific kind, there lies a great inexplicable, which just because of its ultimate character, cannot be merged into anything further—­that is to say, cannot be explained.  ’It is what it is,’ is all that we can say of it:  ‘I am that I am’ is all that it could say of itself.  And it is in referring phenomena to this inexplicable source of physical causation that the theory of Religion essentially consists.  The theory of Science, on the other hand, consists in the assumption that there is always a practically endless chain of physical causation to investigate—­i.e. an endless series of phenomena to be explained.  So that, if we define the process of explanation as the process of referring observed phenomena to their adequate causes, we may say that Religion, by the aid of a general theory of things in the postulation of an intelligent First Cause, furnishes to her own satisfaction an ultimate explanation of the universe as a whole, and therefore is not concerned with any of those proximate explanations or discovery of second causes, which form the exclusive subject-matter of Science.  In other words, we recur to the definitions already stated, to the effect that Religion is a department of thought having, as such, exclusive reference to the Ultimate, while Science is a department of thought having, as such, no less exclusive reference to the Proximate.  When these two departments of thought overlap, interference results, and we find confusion.  Therefore it was that when the religious theory of final causes intruded upon the field of scientific inquiry, it was passing beyond its logical domain; and seeking to arrogate the function of explaining this or that phenomenon in detail, it ceased to be a purely religious theory, while at the same time and for the same reason it blocked the way of scientific progress[20].

This remark serves to introduce one of the chief topics with which I have to deal—­viz. the doctrine of Design in Nature, and thus the whole question of Natural Religion in its relation to Natural Science.  In handling this topic I shall endeavour to take as broad and deep a view as I can of the present standing of Natural Religion, without waiting to show step by step the ways and means by which it has been brought into this position, by the influence of Science.