In October 1798, he was licensed as a preacher, but met with little success. From 1790 to 1802, in addition to holding various tutorships, he occupied himself with historical and philosophical studies. Finding little prospect of a career in Scotland, in 1802 he went to London, in company with Sir John Stuart, then member of parliament for Kincardineshire, and devoted himself to literary work. From 1803 to 1806, he was editor of an ambitious periodical called the Literary Journal, which professed to give a summary view of all the leading departments of human knowledge. During this time he also edited the St James's Chronicle, belonging to the same proprietor. In 1804, he wrote a pamphlet on the corn trade, arguing against a bounty on the exportation of grain. In 1805, he published a translation (with notes and quotations) of CF Villers's work on the Reformation, an unsparing exposure of the alleged vices of the papal system. In 1805 he married Harriet Burrow, whose mother, a widow, kept what was then known as an establishment for lunatics in Hoxton. He then took a house in Pentonville, where his eldest son, John Stuart Mill, was born in 1806. About the end of this year he began his History of India, which he took twelve years to complete, instead of three or four, as had been expected.
In 1808, he became acquainted with Jeremy Bentham, and was for many years his chief companion and ally. He adopted Bentham's principles in their entirety, and determined to devote all his energies to bringing them before the world. Between 1806 and 1818, he wrote for the Anti-Jacobin Review, the British Review and the Eclectic Review; but there is no means of tracing his contributions. In 1808, he began to write for the Edinburgh Review, to which he contributed steadily till 1813, his first known article being "Money and Exchange." He also wrote on Spanish America, China, Francisco de Miranda, the East India Company, and the Liberty of the Press. In the Annual Review for 1808 two articles of his are traced--a "Review of Fox's History," and an article on "Bentham's Law Reforms," probably his first published notice of Bentham. In 1811 he co-operated with William Allen (1770-1843), a Quaker and chemist, in a periodical called the Philanthropist. He contributed largely to every number--his principal topics being Education, Freedom of the Press, and Prison Discipline (under which he expounded Bentham's Panopticon). He made powerful onslaughts on the Church in connection with the Bell and Lancaster controversy, and took a prominent part in the discussions that led to the foundation of the University of London in 1825. In 1814 he wrote a number of articles, containing an exposition of utilitarianism, for the supplement to the fifth edition of the Encyclopædia Britannica, the most important being those on "Jurisprudence," "Prisons" and "Government."
In 1818, the History of India was published, and obtained a great and immediate success. It brought about a change in the author's fortunes. The year following he was appointed an official in the India House, in the important department of the examiner of Indian correspondence. He gradually rose in rank until he was appointed, in 1830, head of the office, with a salary of £1900, raised in 1836 to £2000.
In the meantime, Mill was busy forging the Classical Ricardian School in economics. An energetic man, it was Mill who encouraged David Ricardo to publish his 1817 treatise on value and distribution and then pushed him to run for Parliament. In 1821, Mill helped found the Political Economy Club in London, which became a stomping ground for Ricardian economists and Benthamite radicals. After Ricardo's death, James Mill, John Ramsey McCulloch and Thomas de Quincey became the high priests of Ricardian economics.
James Mill's Elements of Political Economy, (1821) quickly became the leading textbook exposition of doctrinaire Ricardian economics. As this was compiled from the lectures on political economy he had given to his young son, John Stuart Mill, there were was little that was novel in it -- except for the ill-fated "Wages Fund" doctrine:
From 1824 to 1826, Mill contributed to the Westminster Review, started as the organ of his party, a number of articles in which he attacked the Edinburgh and Quarterly Reviews and ecclesiastical establishments. In 1829 appeared the Analysis of the Phenomena of the Human Mind. From 1831 to 1833, Mill was largely occupied in the defence of the East India Company, during the controversy attending the renewal of its charter, he being in virtue of his office the spokesman of the court of directors. For the London Review, founded by Sir William Molesworth in 1834, he wrote a notable article entitled "The Church and its Reform," which was much too sceptical for the time, and injured the Review. His last published book was the Fragment on Mackintosh (1835).
Mill played a great part also in British politics, and was, more than any other man, the founder of what was called "philosophic radicalism." His writings on government and his personal influence among the Liberal politicians of his time determined the change of view from the French Revolution theories of the rights of man and the absolute equality of men to the claiming of securities for good government through a wide extension of the franchise. Under this banner it was that, the Reform Bill was fought and won. His Elements of Political Economy, which was intended only as a textbook of the subject, shows all the author's precision and lucidity. As Dr J. K. Ingram said, it has the "character of a work of art." It followed up the views of Ricardo, with whom Mill was always on terms of intimacy. By 1911, the Encyclopedia Britanica described it as being of mainly historical interest, "an accurate summary of views that are now largely discarded". Among the more important of its theses are:
By his Analysis of the Mind and his Fragment on Mackintosh Mill acquired a position in the history of psychology and ethics. He took up the problems of mind very much after the fashion of the Scottish Enlightenment, as then represented by Thomas Reid, Dugald Stewart and Thomas Brown, but made a new start, due in part to David Hartley, and still more to his own independent thinking. He carried out the principle of association into the analysis of the complex emotional states, as the affections, the aesthetic emotions and the moral sentiment, all which he endeavoured to resolve into pleasurable and painful sensations. But the salient merit of the Analysis is the constant endeavour after precise definition of terms and clear statement of doctrines. The Fragment on Mackintosh is a severe exposure of the flimsiness and misrepresentations of Sir James Mackintosh's famous Dissertation on the Progress of Ethical Philosophy (1830), and discusses the foundations of ethics from the author's utilitarian point of view.