Evolutionary epistemology holds that our knowledge comes to us not from revelation, as religious traditions maintain; nor from deep reflection by the wise, as in Plato; nor even from crisp experiments that unambiguously reveal nature's secrets, as in the mechanistic view of science that prevailed until this century. Rather, our knowledge evolves—with all the haphazardness and improvisation that 'evolving' implies. In biological evolution, species and their genes evolve as they compete for limited resources, with mutations providing the raw material for change. In evolutionary epistemology, hypotheses and ideas evolve as they compete under pressure from criticism, with intellectual diversity providing the raw material for change. The evolutionary view of knowledge recognizes that, in science, trial and error play as important a role as does mechanistic experimentation. It recognizes that scientific consensus doesn't always march methodically toward a single inevitable conclusion; the consensus often meanders or drifts, and where it comes out on any given day can depend as much on circumstance and fashion, even on personalities, as on nature. (Which is not to say that the results are random; the method of trial and error may be unpredictable in the short term, but in the longer term it produces steady improvement. The path may veer this way or that, but the long-term direction is uphill.) Most important, the evolutionary view recognizes that knowledge comes from a social process. Knowledge comes from people checking with each other. Science is not a machine; it is a society, an ecology. And human knowledge, like the species themselves, is a product of the turmoil of the interreactions of living organisms.
Order emerging as each interreacts with each under rules which are the same for all (order without authority): just as that idea links the great liberal systems, so it also links the great liberal theorists. Darwin is known to have been strongly influenced by the economic ideas of Adam Smith. 'The theory of natural selection,' writes Stephen Jay Gould, a paleontologist and historian of science, 'is a creative transfer to biology of Adam Smith's basic argument for a rational economy: the balance and order of nature does riot arise from a higher, external (divine) control, or from the existence of laws operating directly upon the whole, but from struggle among individuals for their own benefits.' And Adam Smith was deeply familiar with the thinking of the British political liberals (he published The Wealth of Nations in 1776, after all). Yet the most intimate connection between members of the liberal constellation is also the least appreciated: the connection between democracy and science. Indeed, the theory of political liberalism and the theory of epistemological liberalism were fathered by one and the same man, the father of liberalism itself.
John Locke proposed, three hundred years ago, that the legitimacy of a government resides not with the rulers but with the rolling consent of the governed. To the argument that 'no government will be able long to subsist, if the People may set up a new Legislative, whenever they take offence at the old one,' Locke replied that government based on popular consent will be more rather than less stable than a regime in which the ruler is fixed, initial impressions notwithstanding. The genius of Locke (and, later, of Adam Smith and Charles Darwin) was to see, as Plato had not, that social stability does not require social stasis; just the opposite, in fact.
This same John Locke also set on its feet the empirical theory of knowledge. Locke himself never explicitly linked his philosophy of knowledge with his philosophy of politics, but the kinship is not hard to see. To begin with, he was one of the greatest of all the fallibilists (or, in that sense, of the skeptics). Just as noone is absolutely entitled to claim the right to rule, so no one is absolutely entitled to decide what is true. Just as not even a king may infringe on basic rights, so not even the wisest or holiest man may claim to be above error. For any and all of us may be mistaken. 'All men are liable to error,' Locke said. 'Good men are men still liable to mistakes, and are sometimes warmly engaged in errors, which they take for divine truths, shining in their minds with the clearest light.' No: however certain you may feel, however strongly you are convinced, you must check.