With respect to economic method he shifted his position, yet to the end occupied uncertain ground. In the fifth of his early essays he asserted that the method a priori is the only mode of investiga tion in the social sciences, and that the method a posteriori "is altogether inefficacious in those sciences as a means of arriving at any considerable body of valuable truth." When he wrote his Logic he had learned from Comte that the a posteriori method— in the form which he chose to call "inverse deduction"—was the only mode of arriving at truth in general sociology ; and his ad mission of this at once renders the essay obsolete. But, unwilling to relinquish the a priori method of his youth, he tries to establish a distinction of two sorts of economic inquiry, one of which, though not the other, can be handled by that method. Sometimes he speaks of political economy as a department "carved out of the general body of the science of society"; whilst on the other hand the title of his systematic work implies a doubt whether political economy is a part of "social philosophy" at all, and not rather a study preparatory and auxiliary to it. Thus, on the logical as well as the dogmatic side, he halts between two opinions. Notwithstanding his misgivings and even disclaimers, he yet re mained as to method a member of the old school, and never passed into the new "historical" school.
In political philosophy his greatest work was done as an advo cate of liberty. In the treatise On Liberty he shows that political liberty alone is insufficient, that social tyranny may be more grinding than legal tyranny. And he showed consistently that any despotism, however benevolent, must in fact cramp and destroy the development of any people. He was torn all his life between his passion for individual liberty and initiative and his sense of the benefits of social control.
System of Logic (2 vols., 1843 ; gth ed., 1875; "People's" ed., 1884) ; Essays on some Unsettled Questions of Political Economy (1844, ed. 1874) ; Principles of Political Economy (2 vols., 1848; many ed., especially ed. by W. J. Ashley, 1909) ; On Liberty (1859 ; ed. Courtney, 1892, W. B. Columbine, 1903 ; with introd. Pringle-Pattison, 191o) ; Thoughts on )Parliamentary Reform (1859) ; Dissertations and Discussions (i., 1859 ; 1867 ; iv. 1876) ; Considerations on Representative Government (1861 ; 3rd ed. 1865) ; Utilitarianism (1863) ; Examination of Sir W. Hamilton's Philo sophy (1865) ; Aug. Comte and Positivism (1865, ed. 1908) ; Inaugural Address at the University of St. Andrews (1867) ; England and Ireland (1868) ; Subjection of Women (1869; ed. with introd. by Stanton Coit, 1906) ; Chapters and Speeches on the Irish Land Question (1870). The Autobiography appeared in 1873 (ed. 5908), and Three Essays on Religion (1874). Many of these have been translated into German, and there is a German edition by Th. Gomperz (12 vols., 1873-80) . A
convenient edition in the New Universal Library appeared between 1905 and 1910.
Biographical and Critical.—Many of Mill's letters are published in Mrs. Grote's life of her husband, in I)uncan's Life of Herbert Spencer, in the Memories of Caroline Fox, and in Kingsley's letters. There are also editions of the correspondence with Gustave d'Eichtal and Comte (specially that of Levy-Bruhl, 1899). By far the most illuminating col lection is that of Hugh Elliott, Letters of John Stuart Mill (2 vols., 191o), which contains letters to John Sterling, Carlyle, E. Lytton Bulwer (Lord Lytton), John Austin, Alex. Bain, and many leading French and German writers and politicians. These letters are essential to an understanding of Mill's life and thought. Besides the Auto biography and many references in the writings of Mill's friends (e.g. Alex. Bain's Autobiography, 1904), see further A. Bain, John Stuart Mill, a Personal Criticism (1882) ; Fox Bourne, Life of J. S. Mill (1873) ; John (Viscount) Morley, Miscellanies (1877), ii. 239-327; J. E Cairnes, J. S. Mill (1873), on economic theories, W. L. Court ney, Metaphysics of J. S. Mill (1879) and Life (1889) ; Douglas, John Stuart Mill, a Study of his Philosophy (1895), and Ethics of J. S. Mill (1897) ; Albee, Hist. of Eng. Utilitarianism (1902) ; Sir Leslie Stephen, The English Utilitarians (19oo) ; J. MacCunn, Six Radical Thinkers (1907) ; Fred. Harrison, Tennyson, Ruskin, Mill (1899) ; John Watson, Comte, Mill and Spencer (1895) ; T. Whittaker, Comte and Mill (1905) ; Charles Douglas, J. S. Mill, a Study of his Philosophy (1895) ; J. Rickaby, Free Will and Four English Philosophers (1906) ; J. M. Robertson, Modern Humanists (1891) ; D. G. Ritchie, Principles of State Interference (1891) ; W. Graham, English Political Philosophy from Hobbes to Maine (1899). There are also a number of valuable French and German criticisms, e.g., Taine, Positivisme anglais, etude sur Stuart Mill (Paris, 1864) ; F. A. Lange, Mills Ansichten fiber die soziale Frage (Duisburg, 1866) ; Littre, A. Comte et Stuart Mill (3rd ed., Paris, 1877) ; Cauret, Philosophie de Stuart Mill (Paris, 1885) ; Gomperz, John S. Mill, ern Nachruf (Vienna, 1889) ; S. Sanger, J. S. Mill, rein Leben und Lebenswerk (Stuttgart, 1901) ; S. Becher, Erkenntnisthe oretische Untersuchungen zu Stuart Mills Theorie der Kausalitiit (1906) ; E. M. Kantzer, La Religion de J. S. Mill (1906) ; F. Degenfeld Schonburg, Die Lohntheorien von Adam Smith, John Stuart Mill, etc. (1914) ; E. Wentscher, Das Problem des Empirismus, dargest. an J. S. Mill (1922) ; B. Alexander, J. St. Mill und der Empirismus (1927) . See also histories of modern philosophy for later criticisms and devel opments of Mill's ideas.
See further LOGIC (Historical Sketch) ; PSYCHOLOGY ; ASSOCIATION OF IDEAS.