is here extended (if it be an extension) to that to which the logic has reference in the existing world. One is here following Spencer, who claims[47] that 'Logic is a science pertaining to objective existence'. On these terms the constitution of any system is the ground of the properties, states, and happenings in that system regarded as isolated. But the changes or properties will be also in relation to surrounding things or systems. These changes, or modifications of change, in relation to external things or events, may properly be said to be conditioned; and we may well restrict the term conditions to influences outside the constitution as ground. Of course, if we accept this usage, we must not speak, with Mill, of the constitution of any system as the condition of its inherent changes or properties. That is why we need some such word and concept as ground. Now we may fix our attention on any constituent part of some natural system and make that part the centre of our interest. That part may be changing in virtue of its constitution; and the rest of the system, regarded as external to this selected part, must therefore be regarded as conditioning. It is a matter of convenience for purposes of scientific interpretation whether we select a larger or a smaller system-group and discuss its constitutional character. Thus we may think of the constitution of the solar system, or of that of the sun's corona; of the constitution of an organism or of that of one of its cells; of the constitution of a complex molecule or of that of an atom therein. We have here reached, or nearly reached, the limiting case in one direction—that of restricting our field of inquiry. The limiting case in the other direction is, I suppose, the universe. But could we so expand our thought as to embrace, if that were possible, the whole universe, then there are no conditions; for ex hypothesi there is nothing for science outside the universe. We have reached the limiting concept. Hence, for science, the constitution of nature is the ultimate ground of all that is or happens.

Let us now see how we stand. Consider the following statements:

1. The Unknowable is the cause of all the phenomena we observe.

2. The constitution of gunpowder is the cause of its explosiveness.[48]

3. The fall of a spark was the cause of the actual explosion of the powder.[49]

Or these:

1. Life is the cause of all vital manifestations.

2. The inherited nature of a hen's egg is the cause of its producing a chick and not a duckling.

3. The cause of the development of the chick embryo is the warmth supplied by the incubating mother.[50]

In each case the reference under (1) is to a transcendent cause which produces the phenomena under consideration. I suggest that the word Source should here be used instead of cause. In each case the reference under (2) is to the nature or constitution of that within which some process occurs. I suggest that the word ground should here be used instead of cause. In each case the reference under (3) is to some external influence. I suggest that the word condition should here be used instead of cause. We thus eliminate the word cause altogether. But since, in nine cases out of ten, the conditions, or some salient condition, is what is meant by cause in popular speech, and in the less exact sciences, the word cause may perhaps be there retained with this particular meaning. These are of course merely suggestions towards the avoidance of puzzling ambiguity. One could wish that Spencer could have thought out some such distinctions to help his sorely perplexed readers.

One could wish, too, that he had devoted his great powers of thought to a searching discussion of the different types of relatedness which are found in nature, and to a fuller consideration of a synthetic scheme of their inter-relatedness. It is imperative that our thought of relations should have a concrete backing. 'Every act of knowing', says Spencer, 'is the formation of a relation in consciousness answering to a relation in the environment.' But the knowledge-relations are of so very special a type; and the relations in the environment are so many and varied. Much more analysis of natural relations is required than Spencer provides. I do not mean, of course, that there is any lack of analysis—and of very penetrating analysis—in the Psychology, the Biology, the Sociology, and the Ethics. I mean that in First Principles, which must be regarded as his general survey of the philosophy of science, there is no searching analysis of the salient types of relationship which enter into the texture of this very complex world. Such omnibus words as differentiation, integration, segregation, do duty in various connexions with convenient elasticity of meaning to suit the occasion. But apart from qualifying adjectives,[51] such as astronomic, geologic, and so on up to artistic and literary, there is too little attempt at either a distinguishing of the types of relatedness or at a relationing of the relations so distinguished. One just jumps from one to another after a break in the text, and finds oneself in a wholly new field of inquiry. Little but the omnibus terminology remains the same. Nor does the Essay on the Classification of the Sciences, with all its tabulation, furnish what is really required. What one seeks to know is how those specific kinds of relatedness which characterize the successive phases of evolutionary progress, inorganic, organic, and superorganic, differ from one another and how they are connected. This one does not find. The impression one gets, here and elsewhere, is that all forms of relatedness must somehow, by the omission of all other specific characters, be reduced to the mechanical type. This, no doubt, is unification of a sort. But is it the sort of unification with which a philosophy of science should rest content?

It may be said that unification can only be reached by digging down to some ubiquitous type of relation which is common to all processes throughout the universe at any stage of evolution. But what, on these terms, becomes of evolution itself as a problem to be solved? Surely any solution of that problem must render an account of just those specific modes of relatedness which have been ignored in digging down to the foundations. Surely there must be unification of the superstructure as well as of the substructure. Here and now is our world, within the texture of which things stand to each other in such varied relations, though they may be reducible to a few main types. There, in the faraway part, was the primitive fire-mist, dear to Spencer's imagination, in which the modes of relationship were so few and so simple, and all seemingly of one main type. How do we get in scientific interpretation from the one to the other? Will it suffice to breathe over the scene the magic