href="@public@vhost@g@gutenberg@html@files@37513@[email protected]#Footnote_31_31" class="fnanchor pginternal" tag="{http://www.w3.org/1999/xhtml}a">[31] that 'motion set up in any direction is itself a cause of further motion in that direction since it is a manifestation of a surplus force in that direction'; and elsewhere[32] that 'the momentum of a body causes it to move in a straight line and at a uniform velocity'. A distinction is drawn between cause and conditions. But both produce effects, and only on these terms can there be that 'proportionality or equivalence between cause and effect' on which Spencer insists.[33] There is, however, scarcely a hint of what constitutes the difference between cause and conditions, save in so far as he speaks[34] of 'those conspicuous antecedents which we call the causes' and 'those accompanying antecedents which we call the conditions'. Many of the details of his treatment I find most perplexing; but to recite examples would be wearisome. And then, in the ninth and tenth articles of the Spencerian creed, cause plays a somewhat different part. For, there, the instability of the homogeneous and the multiplication of effects are given as the chief causes which 'necessitate' that redistribution of matter and motion of which evolution is one phase. Similarly, as I have noted above, in 'Progress: its Law and Cause', the fundamental attribute of all modes of change—that every cause produces more than one effect—is itself spoken of as a cause, and likened to 'gravitation as the cause of each of the groups of phenomena which Kepler formulated'. In these cases a generalization is regarded as the cause of the phenomena from which the generalization is drawn. But sometimes it is spoken of as the reason for the phenomena.[35] Here again, however, as throughout his work, reference to Source is close at hand. Hence, in place of the words cause and force, the word agency[36] sometimes stands for that which produces effects; or the word factor may be used. Thus we are told[37] of phenomena continually complicating under the influence of the same original factors'; and we meet with the argument (contra Huxley) that states of consciousness are factors, that is, they 'have the power of working changes in the nervous system and setting up motions'.[38] Always close at hand, constantly underlying Spencer's thought, is the notion of power which works changes. In his treatment of the philosophy of science we are never far from the noumenal Source of phenomena.

'For that interpretation of things which is alone possible for us this is all we require to know—that the force or energy manifested, now in one way now in another, persists or remains unchanged in amount. But when we ask what this energy is, there is no answer save that it is the noumenal Cause implied by the phenomenal effect.'[39]

Was it partly with Spencer in view that Mr. Bertrand Russell recently urged[40] that the word cause 'is so inextricably bound up with misleading associations as to make its complete extrusion from the philosophical vocabulary desirable'? Professor Mach[41] had previously expressed the hope 'that the science of the future will discard the use of cause and effect as formally obscure'. And as long ago as 1870 W. K. Clifford[42] tried to show in 'what sort of way an exact knowledge of the facts would supersede an enquiry after the causes of them'; and urged that the hypothesis of continuity 'involves such an interdependence of the facts of the universe as forbids us to speak of one fact or set of facts as the cause of another fact or set of facts'. Such views may, perhaps, be regarded as extreme; and the word cause is not likely to be extruded from the vocabulary of current speech, of the less exact branches of science, or of general discussions of world-processes. Still, a philosophy of science must take note of this criticism of the use of a term which is, to say the least of it, ambiguous. We must at any rate try to get rid of ambiguity. Now we live in a world of what, in a very broad and inclusive sense, may be called things; and these things are in varied ways related to each other. (I must beg leave to assume, without discussion, that the relatedness of things is no less constitutive of the world with which a philosophy of science has to deal than the things which are in relation.) And when things stand in certain kinds of relatedness to each other changes take place. The trouble is that the kinds of relatedness are so many and the kinds of change are also so many! Spencer tried to reduce all kinds of relatedness to one quasi-mechanical type; and he signally failed—or shall I say that he succeeded only by ignoring all the specific differences on the one hand, and, on the other hand, by so smudgy an extension of the meaning of mechanical and physical terms as to make them do duty in every conceivable connexion?

So long as we can deal with simple types of relatedness, such as that which we call gravitative, in any given system of things regarded as isolated, we can express in formulae not only the rate of change within the system, but also the rate at which the rate of change itself changes. And these formulae are found to be generally applicable where like things are in a like field of relatedness. So that Spencer's persistence of force (at least in one of its many meanings) is replaced in such cases by sameness of differential equations. And in such cases we have no need for the word cause. Of course the value of the constants in any such formula depends upon the nature of the field of relatedness and of the things therein; and only certain systems, in which the relations are simple, or are susceptible of simplification, can be dealt with, at present, in this manner. It is imperative to remember that not only the rate of change but the kind of change differs in