Rational cosmology up to the seventeenth century presented a coherent picture of the workings of the planetary system without any concern for the origins and development in time of this system. For Aristotle the heavens were unchanging and incorruptible, possessing no origin and experiencing no evolution. Change of place was the only alternation that could be ascribed to the planets. In the Middle Ages this tenet of Aristotelian philosophy led to some conflict with Christian theology since Christians believed that the world had been created by God and that only God was eternal and changeless. Although theologically unacceptable, the Aristotelian conception largely prevailed in scientific astronomy and was a prominent feature of the Copernican-Newtonian world picture.

In the eighteenth century the nebular hypothesis was advanced by Kant and Laplace to explain the genesis of the solar system. Ideas of origin and evolution became things of increasing scientific concern and achieved a dominant place in such sciences as biology and geology. However, as the study of the universe as a whole shifted its focus from the solar system to the stars and nebulae, these ideas receded into the background; there simply was not enough information about the large-scale nature of the universe, and speculations about its origin were hazy at best. All of this changed with the discovery of universal expansion and the microwave background radiation. The traditionally distinct subjects of cosmology and cosmogony, of the nature and structure of the universe on the one hand and the origin and development of the universe on the other, were shown to be coextensive. For the first time in human history it became possible to move beyond the psychological formulations of religious doctrine and make meaningful statements about the creation and evolution of the whole universe.


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