Modern materialists rightly do not bring God into the question. Their mode of argument takes another form; but it remains to be seen if, at bottom, it is not the same as the other. It simply consists in affirming that up till now we know certain properties of matter only, but that science every day discovers new ones; that matter is a reservoir of unknown forces, and that it is not impossible that the origin of psychical forces may yet be discovered in matter. This idea is clearly hinted at by Littre. The physicist Tyndall gave it a definite formula when he uttered at the Belfast Congress this phrase so often quoted: "If I look back on the limits of experimental science, I can discern in the bosom of that matter (which, in our ignorance, while at the same time professing our respect for its Creator, we have, till now, treated with opprobrium) the promise and the power of all forms and qualities of life." The opponents of the doctrine have not ceased to answer that the matter of to-morrow, like the matter of to-day, can generate none but material effects, and that a difficulty is not solved by putting off its solution to some indefinite date in our scientific evolution: and it certainly seems that the counter-stroke is decisive, if we admit the principle of heterogeneity with its natural consequence. We will now criticise the above doctrine by making use of the ideas I have above enunciated. The criticism we have to apply to materialism is not the same as that just summarised. The axis of the discussion changes its position. In the first place, I reproach materialism with presenting itself as a theory of the generation of the consciousness by the object. We have already reproached idealism with putting itself forward as a theory of the generation of the object by the consciousness. The error of the two systems is produced in a converse direction, but is of the same gravity. The consciousness and its object, we say yet again, constitute the widest division it is possible to effect in the domain of cognition; it is quite as illegitimate to reduce the first term to the second as to reduce the second to the first. To reduce one to the other, by way of affiliation or otherwise, there must first be discovered, then, an identity of nature which does not exist.