299. The modern followers of Hume may perhaps seek refuge in the consideration that though the relation of cause and effect between objects is not one in the way of resemblance or one of which the idea is given by comparison of the objects, it yet results from comparisons, which may be supposed to act like chemical substances whose combination produces a substance with properties quite different from those of the combined substances, whether taken separately or together. Some anticipation of such a solution, it may be said, we find in Hume himself, who is aware that from the repetition of impressions of sense and their ideas new, heterogeneous, impressions--those of ‘reflection’--are formed. Of this more will be said when we come to Hume’s treatment of cause and effect as a ‘natural relation.’ For the present we have to enquire what exactly is implied in the comparisons from which this heterogeneous idea of relation is derived. If we look closely we shall find that they presuppose a consciousness of relations as little reducible to resemblance, _i.e._ as little the result of comparison, as that of cause and effect itself. It has been already noticed how Hume treats the judgment of proportion between figures as a mere affair of sense, because such relation depends entirely on the ideas compared, without reflecting that the existence of the figures presupposes those relations of space to which, because (as he admits) they do not depend on the comparison of ideas, the only excuse for reckoning any relation sensible does not apply. In the same way he contents himself with the fact that the judgment of cause and effect implies a comparison of present with past experience, and may thus be brought under his definition of ‘philosophical relation,’ without observing that the experiences compared are themselves by no means reducible to comparison. We judge that an object, which we now find to be precedent and contiguous to another, is its cause when, comparing present experience with past, we find that it always has been so. That in effect is Hume’s account of the relation, ‘considered as a philosophical one:’ and it implies that the constitution of the several experiences compared involves two sorts of relation which Hume admits not to be derived from comparison, _(a)_ relation in time and place, _(b)_ relation in the way of identity. Observation of succession already goes beyond sense.