=1.= The doubt comes from misleading representations of the relativity of knowledge. Unquestionably there is a sense in which our knowledge may justly be said to be "relative." It is not absolute, unconditioned or unlimited. We can know only as we have facilities for knowing, and under the conditions and aspects in which objects are presented to them. We are restricted to the modes and degrees of our given capacities. There are probably many realities about us of which we can know nothing. We have no organs for their perception. Even the things that we do know reach off into transcendent relations. Philosophy has long confessed the relative character of our knowledge. Even the percepts of sense-experience, say for instance, of sight or hearing, when analyzed in physical science are found to be, in their objective cause or material conditions, somewhat different from the simple report of the organ of sense--color being the subjective sensation of light-rays on the retina of the eye, and sound the effect of vibrations of the atmosphere upon the sensorium. But in recent times various theories have represented our knowing faculties as largely untrustworthy and their data as invalid in spheres where their functions appear most certain and explicit. Locke gave basis for a movement in this direction by teaching that the immediate objects of the mind are not things, but "ideas." Berkeley's idealism repudiated the sufficiency of sense-perception to prove the objective existence of the material world. Hume questioned the substantial existence of both matter and mind. In the view of Kant human knowledge reaches only to "phenomena," the appearance of things, while the things as they are "in themselves" can not be known. The mind projects and imposes its own subjective forms of thought upon the universe. Sir Wm. Hamilton, Dean Mansel, J. S. Mill, Alexander Bain and Herbert Spencer have developed theories, variously modified but agreeing in this, that even our necessary forms of rational perception are not to be held as standing for more than relative truth, _i. e._ subjective impressions in our minds in the presence of environment. Doubt is cast upon the point whether what is true to our necessary or actual thought is also really true for the objective world. The teaching will be best understood by several quotations. Sir Wm. Hamilton, though a natural realist, influenced by the speculations of Kant, while acknowledging an underlying reality for phenomena, taught that we can never know them except "under modifications determined by our own faculties."[33]