whole range of the possible. But we know that Mind is a possible entity, while we have no certain knowledge of any other possible entity. Hence we are justified in saying, It is possible that Force and Matter may be identical with the only entity which we know as certainly possible; but forasmuch as we do not know the sum of possible entities, we have no means of calculating the chances there are that what we know as Force and Matter are identical in nature with Mind. Still, that there is _a_ chance we cannot dispute; all we can assert is, that we are unable to determine its value, and that it would be a mistake to suppose we can do so, even in the lowest degree, by Mr. Spencer's test of inconceivability. Nevertheless, the fact that there is such a chance renders it in some indeterminate degree more probable that what we know as Force and Matter are identical with what we know as Mind, than that what we know as oxygen and hydrogen are identical with what we know as water. So that to this extent the essential doctrine of Materialism is "ruled out" in a further degree by the philosophy of the Unknowable than is the chemical doctrine of equivalents. But, of course, this indefinite possibility of what we know as Force and Matter being identical with what we know as Mind does not neutralise, in any determinable degree, the considerations whereby Materialism in its present shape infers that what we know as Force and Matter are probably distinct from what we know as Mind. But I see no reason why Materialism should be restricted to this "its present shape." Even if we admit to the fullest extent the validity of Mr. Spencer's argument, and conclude with Professor Clifford as a matter of probability that "the universe consists entirely of Mind-stuff," I do not see that the admission would affect Materialism in any essential respect. For here again the admission would amount to little else, so far as Materialism is directly concerned, than a change of terminology: instead of calling objective existence "Matter," we call it "Mind-stuff." I say "to _little_ else," because no doubt in one particular there is here some change introduced in the speculative standing of the subject. So long as Matter and Mind, _x_ and _y_, are held to be antithetically opposed in substance, so long must Materialism suppose that a connection of _causality_ subsists between the two, such that the former substance is _produced_ in some unaccountable way by the latter. But when Matter and Mind, _x_ and _y_, are supposed to be identical in substance, the need for any additional supposition as to a causal connection is excluded. But unless we hold, what seems to me an uncalled-for opinion, that the essential feature of Materialism consists in a postulation of a causal connection between _x_ and _y_, it would appear that the only effect of supposing _x_ and _y_ to be really but one substance _z_, must be that of _strengthening_ the essential doctrine of Materialism--the doctrine,