I suppose one of the basal truths in his philosophy of science is for Spencer the universality of connexion between cause and effect. Now let us eliminate Source as the Ultimate Cause (so far as that is possible in Spencer); let us restrict our attention to cause and effect in the realm of the knowable. When we try to do this we find his statements concerning them scarcely less puzzling than those that refer to force, with which cause is so often identified. Thus we are told[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.