he Enlightenment was a period of previously unheard of enquiry and speculation—a quest to discover the nature of man and the nature of things through the powers of Reason. Rationality was lauded as the sole arbiter of truth; as the only sound basis for knowledge, taste, ethics and government. Having its origins in the seventeenth century, the Enlightenment encompassed the scientific revolution as well as the French and American Revolutions, it was dubbed “The Age of Reason,” by Thomas Paine, who spoke for many when he declared that “the most formidable weapon against errors of every kind is Reason. I have never used any other, and I trust I never shall.” The Age of Reason spoke most directly, though, to the nature of man. Thus, although the likes of Copernicus, Galileo, Kepler and Newton looked to the stars, what they saw there altered their view of mankind—for the briefest of moments they unsettled the smug certainty that we humans were the centre of the Creator’s universe just as we are of our own. Our nature is not such that our self-obsession was for long disturbed however, and Enlightenment scholars consoled themselves with the full knowledge that even while we might not adequately speculate on the nature of God and his intentions through reasoned inquiry, it was the nature of man, after all, that was—and remains—the most interesting of questions.
Indeed, there is no greater question that this: What is the nature of man? This was true for Enlightenment scholars no less than for ourselves, troubled as we are by the sublime promises of genetic engineering, psychotropic drugs, and the deep ethical problems inherent to our reflections upon the extent and limits of autonomy. But how might one even begin to answer such a question as that posed by the nature of man? The French philosopher René Descartes had drilled this down to the one presumption that he believed that man was entitled to make about himself—the fact of his existence. He was sensible of himself by virtue of his Reason—“I think, therefore I am,” he had declared in consequence; in this great world of enquiry there was no other point of certainty. “Give me a lever long enough and a place to stand and I will move the Earth” the Greek mathematician Archimedes is supposed to have said—here was somewhere to stand.
With reason as a starting point the world could indeed move, Copernicus had proven this much, at least. Turning to man, though, what more might be said—if one could divine the nature of man one might also determine how he should live—reason had made man a moral animal, or so it seemed legitimate to presume. But how had it done so? This was a compelling question indeed! The question of the nature and the origin of the moral sentiments taxed some of the greatest minds of the enlightenment—and we shall have cause to consider the views of a number of them in this book: the associationist philosophers Adam Smith, David Hume and Erasmus Darwin, of course, as well as Nicholas de Condorcet and the English utilitarians William Godwin and Thomas Robert Malthus. These men were followed in this enquiry and in this tradition by Jeremy Bentham, James Mill and his son John Stuart Mill, the last of whom became a foundational figure in philosophical radicalism. The moral nature of man was no mere topic of idle curiosity, but rather became a fundamental question in consideration of what constituted a right and just polity. “What is the nature of man, and in consequence, how might he live?” This was the question they addressed themselves to, and the question that is my focus in this book. Further, was the nature of man fixed and unchangeable? And what did this say to the way in which he was governed? Indeed, did man make his environment, or was he made by it? All these questions and more came rushing in like a flood—rising to the task, these and other men provided no end of answers.It is in this context that I will consider the work of the eminent nineteenth-century naturalist Charles Darwin. His 1859 book On the Origin of Species once again shook the foundations of the world. English Victorians wrestled with it, uncertain as to which was the most disturbing of the books many implications—the common ancestry with apes, or the fact that our very existence was the outcome of contingency and chance?
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 Thomas Paine, The Age of Reason, Being an Investigation of True and Fabulous Theology, (Philadelphia, 1794), p.1.
 These moral questions and the challenge posed by our increasing focus, at least in the West, upon autonomy have been most recently posed by philosophers from both the right and the left of the political spectrum—Leon Kass, Life Liberty and the Defense of Human Dignity (2002)and Frances Fukuyama, Our Post-Human Future (2002) on the one hand, and Bill McKibbin Enough and Troy Duster, The Backdoor to Eugenics to name only a few from the other.
 René Descartes, Discourse on Method, (1637).