Scientific method played the central role in bringing about the revolutionary world view ushered in by such names as Roger Bacon, Descartes, and Galileo, which by the time of the seventeenth-century "Age of Enlightenment" had triumphed as the guiding philosophy of Western intellectual culture. No longer was permissible Truth constrained by interpretation of the Scriptures, readings of Aristotle and the classics, or logical premises handed down from the medieval Scholastics. Unencumbered by dogma and preconceptions of how reality had to be, Science was free to follow wherever the evidence led and uncover what it would. Its successes were spectacular indeed. The heavenly bodies that had awed the ancients and been regarded by them as deities were revealed as no different from the matter that makes up the familiar world, moved by the same forces. Mysteries of motion and form, winds and tides, heat and light were equally reduced to interplays of mindless, mechanical processes accessible to reason and predictable by calculation. The divine hand whose workings had once been invoked to explain just about everything that happened was no longer necessary. Neither, it seemed to many, were the traditional forms of authority that presented themselves as interpreters of its will and purpose. The one big exception was that nobody had any better answers to explain the baffling behavior of living things or where they could have come from.
A widely held view is that Charles Darwin changed the world by realizing that life could appear and diversify by evolution. This isn't really the way it was, or the reason he caused so much excitement. The notion of life appearing spontaneously through some natural process was not in itself new, being found in such places as the Babylonian creation epic, Enuma Elish, and ancient Chinese teachings that insects come from nothing on the leaves of plants. Ideas of progressive development are expressed in the philosophies of Democritus and Epicurus, while Amaximander of Miletus (550 b.c.) held that life had originated by material processes out of sea slime—in some ways anticipating modern notions of a prebiotic soup. Empedocles of Ionia (450 b.c.) proposed a selection-driven process to account for adaptive complexity, in which all kinds of monstrosities were produced from the chance appearance of various combinations of body parts, human and animal, out of which only those exhibiting an inner harmony conducive to life were preserved and went on to multiply. The line continues down through such names as Hume, who speculated that the random juggling of matter must eventually produce ordered forms adapted to their environment; Lamarck, with his comprehensive theory of evolution by the inheritance of characteristics acquired through the striving of the parents during life; to Charles Darwin's grandfather, Erasmus Darwin, who studied the similarities of anatomy between species and speculated on common ancestry as the reason.
The full title of Charles Darwin's celebrated 1859 publication was The Origin of Species By Means of Natural Selection or the Preservation of Favoured Races in the Struggle for Life. The case it presents hardly needs to be elaborated here. Essentially, species improve and diverge through the accumulation of selected modifications inherited from common ancestors, from which arise new species and eventually all of the diversity that makes up the living world. The solution that Darwin proposed was simple and elegant, requiring three premises that were practically self-evident: that organisms varied; that these variations were inherited; and that organisms were engaged in a competition for the means of survival, in the course of which the better equipped would be favored. Given variations, and given that they could be inherited, selection and hence adaptive change of the group as a whole was inevitable. And over sufficient time the principle could be extrapolated indefinitely to account for the existence of anything.
None of the ingredients was especially new. But in bringing together his synthesis of ideas that had all been around for some time, Darwin provided for the first time a plausible, intellectually acceptable naturalistic and materialist explanation for the phenomenon of life at a time when many converging interests were desperately seeking one. Enlightenment thinkers, heady with the successes of the physical sciences, relished the opportunity to finish the job by expelling the last vestiges of supernatural agency from their world picture. The various factions of the new political power arising out of commerce and manufacturing found common ground from which to challenge the legitimacy of traditional authority rooted in land and Church, while at the same time, ironically, the nobility, witnessing the specter of militant socialist revolution threatening to sweep Europe, took refuge in the doctrine of slow, imperceptible change as the natural way of things. Meanwhile, the forces of exploitation and imperialism, long straining against the leash of moral restraint, were freed by the reassurance that extermination of the weak by the strong, and domination as the reward for excellence were better for all in the long run.
There was something in it for everyone. Apart from the old order fighting a rearguard action, the doctrine of competitive survival, improvement, and growth was broadly embraced as the driving principle of all progress—the Victorian ideal—and vigorously publicized and promoted. Science replaced the priesthood in cultural authority, no longer merely serving the throne but as supreme interpreter of the laws by which empires and fortunes flourish or vanish. Darwin's biographer, Gertrude Himmelfarb, wrote that the theory could only have originated in laissez-faire England, because "Only there could Darwin have blandly assumed that the basic unit was the individual, the basic instinct self-interest, and the basic activity struggle."1