Some have said that the history of the Western world is a battle between the ideas of Plato and those of Aristotle, between the otherworldly and the this-worldly, between the mystical and the rational.1 The Enlightenment was an age when the Aristotelian approach of observation and logic generally prevailed, when a great many thinkers—for the first time since ancient Greece—truly prized their minds as the means by which to understand and shape the world. Isaac Newton discovered mathematical principles governing natural phenomena, Benjamin Franklin turned disparate observations about electricity into a unified scientific theory, Captain James Cook explored distant lands, Denis Diderot organized a mass of new knowledge in the world’s first encyclopedia. Instead of basking in thoughts of the glory of an alleged afterlife, a number of great men turned their focus to the here and now, toward making this world as good a place as possible for human life.
Some embraced this scientific mind-set and applied it to understanding man himself, his means of knowledge, ethics, and the origin, purpose, and proper structure of government. The result of their efforts was most eloquently expressed in the Declaration of Independence: “We hold these truths to be self-evident, that all men are created equal,” wrote Thomas Jefferson, that they have “certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness. — That to secure these rights, Governments are instituted among Men, deriving their just powers from the consent of the governed.” The distinctive social and political philosophy of the Enlightenment enshrined liberty, so the system of thought that men developed to support and defend it became known as liberalism.
Importantly, however, this political philosophy did not originate with Jefferson or his contemporaries. As Jefferson wrote, “the object of the Declaration” was “not to find out new principles, or new arguments, never before thought of,” but rather “to be an expression of the American mind.” “[A]ll its authority,” he conceded, “rests then on the harmonizing sentiments of the day.”2 And as he readily pointed out, one of the primary shapers of the American mind was John Locke.3 Locke (1632–1704) was at the forefront of Enlightenment thinkers who advanced an experimental, this-worldly approach to knowledge, science, and philosophy. Although he was not the first to advance a theory of natural rights, his defense of rights was the most systematic, clear, and comprehensive—and, consequently, the most influential.4
Sons of Liberty leader Samuel Adams bolstered his arguments for the rights of American colonists with near direct quotations of Locke.5 Alexander Hamilton chastised an adversary for his apparent ignorance of natural rights theory and recommended that he read Locke.6 John Adams cited Locke as an inspiration for his “revolution-principles,” which he said were “the principles of nature and eternal reason” and constituted a rational alternative to docile obedience and bloody anarchy.7
Adams also was influenced deeply by Locke’s ideas about the nature of the mind and our means of acquiring knowledge. So was Benjamin Franklin, who commemorated Locke as “the Newton of the Microcosm” and who relied heavily on Locke’s ideas about education, history, rhetoric, and law in his efforts to establish Philadelphia Academy (known today as the University of Pennsylvania).8
Indeed, if Jefferson or any other writer of the time had intended to express not the “American mind,” but the Western mind or the Enlightenment mind as such, he’d be hard pressed to articulate its “harmonizing sentiments” without invoking the ideas of John Locke. If we want to advance the Enlightenment and live in it today, we must understand Locke’s ideas.
In Pursuit of Useful Truths
Locke so well encapsulated the Enlightenment mind because he passionately pursued any and all knowledge that could be used to enhance human life and happiness. As a friend of his said, what Locke “chiefly loved” were “truths that were useful, and with such fed his mind.”9
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