It is not, however, in any of these precise forms that Hamilton holds the doctrine of the relativity of knowledge. He assumes a middle place between Reid and Kant, and endeavors to blend the subjective idealism of the latter with the realism of the former. "He identifies the _phenomenon_ of the German with the _quality_ of the British philosophy,"[306] and asserts, as a regulative law of thought, that the quality implies the substance, and the phenomenon the noumenon, but makes the substratum or noumenon (the object in itself) unknown and unknowable. The "phenomenon" of Kant was, however, something essentially different from the "quality" of Reid. In the philosophy of Kant, _phenomenon_ means an object as we envisage or represent it to ourselves, in opposition to the _noumenon_, or a thing as it is in itself. The phenomenon is composed, in part, of subjective elements supplied by the mind itself; as regards intuition, the forms of space and time; as regards thought, the categories of Quantity, Quality, Relation, and Modality. To perceive a thing in itself would be to perceive it neither in space nor in time. To think a thing in itself would be not to think it under any of the categories. The phenomenal is thus the product of the inherent laws of our own constitution, and, as such, is the sum and limit of all our knowledge.[307] [Footnote 305: Martineau's "Essays," p. 234.] [Footnote 306: M'Cosh's "Defense of Fundamental Truth," p. 106.] [Footnote 307: Mansel's "Lectures on the Philosophy of Kant," pp. 21, 22.] This, in its main features, is evidently the doctrine propounded by Hamilton. The special modes in which existence is cognizable" are presented to, and known by, the mind _under modifications determined by the faculties themselves_."[308] This doctrine he illustrates by the following supposition: "Suppose the total object of consciousness in perception is=12; and suppose that the external reality contributes 6, the material sense 3, and the mind 3; this may enable you to form some rude conjecture of the nature of the object of perception."[309] The conclusion at which Hamilton arrives, therefore, is that things are not known to us as they exist, but simply as they appear, and as our minds are capable of perceiving them. [Footnote 308: Hamilton's "Lectures on Metaphysics," vol. i. p. 148.] [Footnote 309: Hamilton's "Lectures on Metaphysics," vol. ii. p. 129; and also vol. i. p. 147.]