In On Liberty (1859), John Stuart Mill mentions custom as a bad thing. Custom is what prevents independent thinking. It blocks the inquiry for truth, because it puts conformity to established thinking above testing the possible truth of new ideas. It subjects us to a tyranny of the majority, where we feel bound to accept what most people say because of the moral pressure of knowing that most people think something, and the pain of insisting on a different idea. The pressure of custom is as much a danger to liberty as excessive state power, and the two forces combine in restricting liberty.
One paradoxical outcome is that though Mill wants strong limits on state power, he thinks state power is justified in overcoming ‘barbarism’, which is his justification for colonialism. Even within a developed educated society. Mill worries about those who follow custom rather than rational thought, He is very inclined to identify rational thought with being on the progressive side in politics, which for him means being for free markets, individual freedom, education, and secularism. This leads to a rather contemptuous view of the rationality of people on the other side of the debate as in his famous suggestion that the Conservative Party in Britain was the stupid party. Though he favoured decentralisation and localism in government, he had very little regard for those who wished to maintain local. and regional, languages, cultures and customs. For Mill, it was very much better to be a full part of the greatest language and culture of a nation, and this was closely connected with his notion of rationality. He makes this clear in Considerations on Representative Government (1861) The paradox here is that disregard for custom leads to disregard for certain kinds of liberty, those associated with keeping a minority identity.
Another paradox is that sometimes Mill appeals to custom as a justifiable punitive force. Mill refers to situation where the law should not be involved, but public opinion should be. The main example is of the man who drinks too much too look after his children well. Mill does not think the coercive power of the state should intervene here, but we should keep away from friendship with such a person and put moral pressure on him. In this instance the paradox is that habits which come from custom should be used as a form of social control. The issue in this instance is not of freedom of speech. which is at the centre of Mill’s view of liberty. but appealing to custom in one instance will have spill over effects in other kinds of instance.
In some degree the limited state ideas Mill has come from people who think strength of custom can make state coercion unnecessary. Wilhelm von Humboldt’s Limits of State Action, which Mill quotes several times in On Liberty, sees its ideal of a state with no function other than national defence and internal law and order, includes the idea that peoples who live by custom can achieve this state. Mill’s ideas of the state were less minimal, and there is evidently some tensions in Humboldt about the values of diversity and the values of custom, but this just increases the sense of paradox around opposing both state and moral oppression. Going back further, Montesquieu and Rousseau both linked the freedom of the more pure republic with a lack of much of a state, because citizens follow virtue by habit rather than the coercion of law. Mill, like many, saw Montesquieu as a founder of liberalism and Rosseau as a source of state despotism. The differences and similarities between Rousseau will have to wait for another occasion, but for now I will say that like many Mill is bit too quick in his way of opposing Rousseau and Montesquieu, not completely wrong but not completely right either.
The status of custom, or habit, or public opinion, of whatever way we can think of for referring to moral non-coercive pressures, does provide a paradoxical source of benefit and danger to liberty for Mill. The problem is not unique to him, and we should recognise that public opinion is a way of referring to something changeable and custom refers to something more permanent. Nevertheless, they both refer to moral force, and their duality brings out Mill’s difficulty.