2009 is the 150th anniversary of John Stuart Mill’s ‘On Liberty’ – it’s a work relevant to all non-religious people because of the humanistic approach it takes to human flourishing without religion, and it’s relevant  to religious people as well for the secular political settlement it advocates. I’ve written an article about it in today’s Guardian (p.37) – it’s now available online and below. (As well as On the Origin of Species and On Liberty, 2009 is also the 150th anniversary of George Eliot’s first novel Adam Bede – a good year for humanist publishing!)

This year is being celebrated as Charles Darwin‘s year – the bicentenary of his birth and the 150th anniversary of On the Origin of Species. But 1859 saw the publication of a work just as influential and worthy of celebration, the contents of which are arguably more in danger of being forgotten by us than Darwin’s.

On Liberty was and remains John Stuart Mill’s best-known work. It is, as political philosopher Alan Haworth said in a briefing distributed to parliamentarians this year, “an object lesson in the systematisation of those general principles which most effectively embody the only values most appropriate to a free people”. Mill advances a view based on freedom – freedom of thought, speech and association, underpinned by a respect for the free individual, including respect for the freedom of the individual to differ.

At a time when religion in politics threatens to divide society, On Liberty is a timely reminder that there is a way to conceive of society other than through the communalistic approach to diversity that places “groups” at the centre of policy rather than free individuals. Mill stands for free speech and discussion in all matters, including religious and political ones, because this is how society can test and refine propositions thought to be true – a rebuke to the idea that the law should censor free expression to protect the sensitivities of groups. If groups matter, in Mill’s view, it is because the liberty of individuals to form them matters, and groups can never be allowed to tyrannise or enforce their own dogma on others.

However, On Liberty should be celebrated not just as a political handbook – it addresses, in Mill’s own phrase, “the wellbeing of mankind”. His work contains profound reflections on human flourishing that are a significant contribution to the humanist tradition. Mill’s view is that, “Among the works of man, which human life is rightly employed in perfecting and beautifying, the first in importance surely is man himself.”

He encourages us to value not just experience, but also the discussion and examination of experience, so we can make our choices reflectively, developing “the human faculties of perception, judgment, discriminative feeling, mental activity, and … moral preference.” He encourages us to ask “what would allow the best and highest in me to have fair play, and enable it to grow and thrive?” so we can become “more valuable” to ourselves and “therefore capable of being more valuable to others”. He believes that “human nature is not a machine … but a tree, which requires to grow and develop itself on all sides”.

So, although the principal relevance of On Liberty remains what it points towards as the way to organise ourselves politically, the insights of Mill into the ingredients of the good life for a non-religious person equally call for celebration by humanists in this anniversary year. We might also remember the ways in which Mill’s convictions about the worth and dignity of human life – vital principles for modern humanists – stimulated him in social action, opposition to slavery, and a commendably anachronistic appetite for gender equality.

The ideas Mill advanced in 1859 drew criticism from religious sources in particular. But the political principles he evolved are ones that can be shared today by people of any religion as much as by humanists. The outworking of Darwin’s ideas demonstrated how every one of us is linked on the tree of life – how just a couple of million years ago we were literally one family. The principles of On Liberty can bring us together on the basis of our common humanity in another way. If we want to be free to pursue our own conception of the good life and of human flourishing – religious or non-religious – we have to defend the freedom of others as earnestly as we defend our own. This secular political principle is accessible to people of all traditions and benefits us all.