But now that the notion of _mind_ or _self_, and of _matter_ or not _self_, do exist as common convictions of our race, what is philosophy to make of them? After a great many qualifications and explanations, Mr. Mill has, in his "Logic," summed up his doctrine of Constructive Idealism in the following words: "As body is the mysterious _something_ which excites the mind to feel, so mind is the mysterious _something_ which feels and thinks."[228] But what is this "mysterious something?" Is it a reality, an entity, a subject; or is it a shadow, an illusion, a dream? In his "Examination of Sir Wm. Hamilton's Philosophy," where it may be presumed, we have his maturest opinions, Mr. Mill, in still more abstract and idealistic phraseology, attempts an answer. Here he defines matter as "_a permanent possibility of sensation_,"[229] and mind as "_a permanent possibility of feeling_."[230] And "the belief in these permanent possibilities," he assures us, "includes all that is essential or characteristic in the belief in substance."[231] "If I am asked," says he, "whether I believe in matter, I ask whether the questioner accepts this definition of it. If he does, I believe in matter: and so do all Berkeleians. In any other sense than this, I do not. But I affirm with confidence that this conception of matter includes the whole meaning attached to it by the common world, apart from philosophical, and sometimes from theological theories. The reliance of mankind on the real existence of visible and tangible objects, means reliance on the reality and permanence of possibilities of visual and tactual sensations, when no sensations are actually experienced."[232] "Sensations," however, let it be borne in mind, are but a subordinate species of the genus feeling.[233] They are "states of consciousness"--phenomena of mind, not of matter; and we are still within the impassable boundary of ideal phenomena; we have yet no cognition of an external world. The sole cosmical conception, for us, is still a succession of sensations, or states of consciousness. This is the one phenomenon which we can not transcend in knowledge, do what we will; all else is hypothesis and illusion. The _non-ego_, after all, then, may be but a mode in which the mind represents to itself the possible modifications of the _ego_. [Footnote 228: "Logic," bk. i, ch. iii. § 8.] [Footnote 229: "Examination of Sir Wm. Hamilton's Philosophy," vol. i. p. 243.] [Footnote 230: Ibid., vol. i. p. 253.] [Footnote 231: Ibid., vol. i. p. 246.] [Footnote 232: Ibid., vol. i. pp. 243, 244.] [Footnote 233: "Logic," bk. i. ch. iii. § 3.]