What idea, we may well ask ourselves, did these modern philosophers entertain regarding the pretensions of ancient and mediæval metaphysics? What understanding had they of the spirit in which the natural organs of reason had been exercised and developed in those schools? Frankly, very little; for they accepted from ancient philosophy and from common-sense the distinction between reality and appearance, but they forgot the function of that distinction and dislocated its meaning, which was nothing but to translate the chaos of perception into the regular play of stable natures and objects congenial to discursive thought and valid in the art of living. Philosophy had been the natural science of perception raised to the reflective plane, the objects maintaining themselves on this higher plane being styled realities, and those still floundering below it being called appearances or mere ideas. The function of envisaging reality, ever since Parmenides and Heraclitus, had been universally attributed to the intellect. When the moderns, therefore, proved anew that it was the mind that framed that idea, and that what we call reality, substance, nature, or God, can be reached only by an operation of reason, they made no very novel or damaging discovery. Of course, it is possible to disregard the suggestions of reason in any particular case and it is quite possible to believe, for instance, that the hypothesis of an external material world is an erroneous one. But that this hypothesis is erroneous does not follow from the fact that it is a hypothesis. To discard it on that ground would be to discard all reasoned knowledge and to deny altogether the validity of thought. If intelligence is assumed to be an organ of cognition and a vehicle for truth, a given hypothesis about the causes of perception can only be discarded when a better hypothesis on the same subject has been supplied. To be better such a hypothesis would have to meet the multiplicity of phenomena and their mutations with a more intelligible scheme of comprehension and a more useful instrument of control. [Sidenote: All criticism dogmatic.]