John Stuart Mill was a philosopher, social reformer, parliamentarian (Liberal MP from 1865-8), and campaigner for women's rights.  He was also prophetic in his insistence in the importance of contraception, and was once jailed for distributing leaflets on birth control.  Click here for a history of birth control. Mill would have agreeed with the reformer Richard Carlile's view of the "brute-like tendency of mankind to breed ourselves into increased unhappiness" (1829: A Woman's Book).  Carlile also suffered a six year sentence.

His essay on Utiltarianism builds on the work of Jeremy Bentham, but differs in three important respects: Mill has an idea of happiness much closer to Aristotle's eudaimonia (meaning flourishing or well-being); Mill distinguishes between higher and lower pleasures, and finally, he devotes a whole section of his essay to explaining and defending an idea of justice as an essential part of utilitarian ethics. Nonetheless, Mill's much greater work is "on Liberty" which lays down the value of freedom for a democratic society,and declares boldly: "truth that is not tested is not living truth but dead dogma".

His close relationship with Harriet Taylor was finally consummated when her husband died in 1851.  When she died at Avignon in 1858 he was inconsolable, and when he himself died at Avignon in 1878 was buried next to her.  

As a lifelong radical Mill wasn't very complementary about conservatives:

"What I stated was, that the Conservative Party was, by the law of its constitution, necessarily the stupidest party. Now, I do not retract that assertion; but I did not mean to say that the Conservatives are generally stupid. I meant to say that stupid people are generally Conservative. I believe that is so obviously and universally admitted a principle that I hardly think any gentleman will deny it. (Public and Parliamentary Speeches, 31 May 1866, pp. 85-86.)"

One finds Mill elsewhere also saying that

"Stupidity is much the same the world over. A stupid person's notions and feelings may confidently be inferred from those which prevail in the circle by which the person is surrounded.  (Subjection of Women, Chapter I, p. 273)".

Roger Crisp explains the background to Mill's utilitarianism here.

For a discussion of the legacy of utilitarian ethics for British society click here.