The liberal tradition in politics is, first and foremost, about individual liberty. Although its roots go far back in the history of political thought, liberalism emerged as a distinct political theory as a call for freedom of speech and of thought. As one eminent political theorist observed, freedom of thought ‘is an idea which emerges slowly in the West in the course of the sixteenth and seventeenth centuries; and yet today, in the eyes of the liberal, it is this liberty which is most precious of all’. Right from the outset, the liberal case for freedom of conscience has derived from devotion to human reason.
In Areopagitica: A Speech for the Liberty on Unlicensed Printing (1644), John Milton argued for freedom of conscience and of the press by appealing to reason and truth. ‘Truth’, Milton argued, is ‘our richest Merchandise’. ‘Let her [i.e., truth] and Falsehood grapple; who ever knew truth put to worse, in a free and open encounter?’ Given freedom of speech and thought, truth will win out because, unlike superstition and error, which varies from group to group and time to time, truth appeals to our universal, shared, reason. Hence, proclaimed Milton, ‘Give me the liberty to know, to utter, and to argue freely according to conscience, above all liberties’. Over two hundred years later (1859), John Stuart Mill again appealed to truth and reason in his case for freedom of thought and speech:
The beliefs which we have most warrant for, have no safeguard to rest on, but a standing invitation to the whole world to prove them unfounded. If the challenge is not accepted, or is accepted and the attempt fails, we are far enough from certainty still; but we have done the best that the existing state of human reason admits of; we have neglected nothing that could give the truth a chance of reaching us: if the lists are kept open, we may hope that if there be a better truth, it will be found when the human mind is capable of receiving it; and in the meantime we may rely on having attained such approach to truth, as is possible in our own day. This is the amount of certainty attainable by a fallible being, and this the sole way of attaining it.
Mill is struck by our fallibility: no matter how much we have thought an issue through, we can never be certain that we are correct – it is always possible we have fallen into error. Such fallible creatures, Mill insists, can only suppose their beliefs approach the truth if those beliefs are subject to criticism in free debate. Like Milton, Mill believes that true opinions are more likely to be embraced in free discussion because they appeal to our reason.
Milton and Mill advance classic statements of a basic liberal theme: given freedom of thought, speech and inquiry, our common human reason leads us toward increasing agreement on truths and rejection of falsehoods. Sometimes this is put in terms of the ‘free marketplace of ideas’: in a free competition of ideas, the truth will eventually win out, and the longer the competition goes on, the more truths will be uncovered. Underlying this is the conviction that while we are all subject to various sorts of biases, superstitions, and errors, these differ from one person (or group) to another. My biases and superstitions may appeal to me and some like-minded bigots, but they are unlikely to gain universal acceptance because not everyone shares my biases and superstitions. But, the liberal insists, the powers of reason are shared and universal. Reason is what unites us. In the words of a twentieth-century liberal, ‘[a]ll that man is and all that raises him above animals he owes to his reason’. Overall reason selects the case for what is true rather than what is false.
The exercise of our reason, then, leads us to agree. Mill – and here he speaks for much of the liberal tradition – was thus convinced that one aspect of social progress was convergence on an increasing body of truths.