The two next chapters of Mr Mill, noticing some other minor peculiarities (all of them unfortunate, and one, p. 447, really unaccountable) of Sir W. Hamilton’s Formal Logic; and some Fallacious Modes of Thought countenanced by Sir W. Hamilton (chs. xxiii., xxiv.—­pp. 446, 478), we are compelled to pass over.  We must find space, however, for a few words on the Freedom of the Will (ch. xxv.), which (in Mr Mill’s language, pp. 488—­549), ’was so fundamental with Sir W. Hamilton, that it may be regarded as the central idea of his system—­the determining cause of most of his philosophical opinions.’  Prior to Sir W. Hamilton, we find some writers who maintain the doctrine of Free-will, others who maintain that of Necessity:  each supporting their respective conclusions by reasons which they deem sufficient.  Sir W. Hamilton declares that both the one doctrine and the other are inconceivable and incomprehensible; yet that, by the law of Excluded Middle, one or other of them must be true:  and he decides in favour of Free-will, of which he believes himself to be distinctly conscious; moreover, Free-will is essential (he thinks) to moral responsibility, of which also he feels himself conscious.  He confesses himself, however, unable to explain the possibility of Free-will; but he maintains that the same may be said about Necessity also.  ’The champions of both the two opposite doctrines are at once resistless in attack, and impotent in defence’—­(Hamilton’s ‘Footnotes on Reid,’ p. 602.) Mr Mansel also asserts, even more confidently than Sir W. Hamilton, that we are directly conscious of Free-will—­(p. 503).

Sir W. Hamilton has himself given some of the best arguments against the doctrine of Free-will, in refutation of Reid:  arguments, some of which are here cited by Mr Mill with praise which they well deserve—­(pp. 497, 498).  But Mr Mill’s own reasoning on the same side is of a still higher order, enlarging the grounds previously urged in the last book of his ‘System of Logic,’ He protests against the term Necessity; and discards the idea of Necessity, if it be understood to imply anything more than invariability of antecedence and consequence.  If it mean that, experience proves thus much about antecedents in the world of mind, as in the world of matter:  if it mean more, experience does not prove more, either in the world of matter or in the world of mind:  nor have we any grounds for affirming it in either—­(p. 501.) If it were true, therefore, that consciousness attested Free-will, we should find the testimony of consciousness opposed to a full proof from experience and induction.  But does consciousness really attest what is called Free-will?  Mr Mill analyzes the case, and declares in the negative.