Objection to be made to Christian philosophy is that it is a dualistic system. Christianity holds that there are two realities, two things equally true, equally real. Now to say that truth is of two kinds is to say that there are 2 realities, 2 truths. But this conception is absurd; there cannot be more than one reality, more than one truth. «Realities», «truths» (this last word in its most extensive sense) are not expressions which owe much to logic; nor is it a custom to use them. There cannot be, then, there are not, two realities. Such a conception is impossible. Dualism as a theory of things is a (child) product of philosophic idiocy (childhood).

But it may be added, matter and spirit are realities, but they are realities either (says one theory) of different kinds, or (another will say) of different degrees. The first of these two hipotheses is, I believe, already disproved. For I have already said that two realities are impossible, that reality is understood to be one. Realities of two kinds are two realities and no more. But if it be thought that this is not so and that two realities may be conceived, one as infinite and as eternal, another as finite in space and in time; still there is [an] answer for this and a word against it. In the first place reality (for reality is ever a unitary concept) cannot be at the same time eternal and in time, infinite and in space. It has to be one, or it must be the other or, perhaps, other than either of these. It Cannot be both, for then it would be dual, it would lose its quality of reality.

It would be possible to answer again: reality is thus dual because dually considered. Dually considered — and by whom? By man? — then either all reality is subjective and there is none, and we have Protagoras again. Or then reality is to be considered in itself and, being considered thus, the first thing to be postulated about it is that there is one reality alone. But these two realities may be said to be objective, not made or thought by us. But objective reality is again and as truly one. If two realities be shown to us then either one is an illusion, or both are illusions, and, in these cases, either the other, or something other than both is the reality. Two kinds of realities are then inconceivable; there is only one reality, no more than one truth.

Again, as we have noticed, an hypothesis may be made, that matter and spirit are realities of different degrees. But then, if matter and spirit be realities of different degrees, there are realities of other degrees and we do not take conscience of them. This is extraordinary enough, but it is not sufficient to disprove; there are better things in the same argument. For two, any number of degrees of anything, in any quality, suppose a series in that quality, and a series in any quality supposes an infinite (the quality itself in itself, in the abstract) at the top, and zero of that quality at the foot. Two degrees of reality suppose therefore, if these degrees be truly relative, numerical, none of them is real, the reality is the infinite at the top. There is no reality but reality. On the other hand if these be relative only to each other, if they be two absolutes, one of them is infinity (reality itself) and the other zero (no reality at all). Again is dualism impossible.

It may now be said: duality is transitory, spirit is really the only reality.