Evolution: Topic Index

These topics were written by Dr. Francisco Ayala, Professor of Biological Sciences and Philosophy at the University of California, Irvine. He is a member of the President's Committee of Advisors on Science and Technology, and has been President and Chairman of the Board of the American Association for the Advancement of Science.

I advance three propositions. The first is that Darwin's most significant intellectual contribution is that he brought the origin and diversity of organisms into the realm of science. The Copernican Revolution consisted in a commitment to the postulate that the universe is governed by natural laws that account for natural phenomena. Darwin completed the Copernican Revolution by extending that commitment to the living world.

The second proposition is that natural selection is a creative process that can account for the appearance of genuine novelty. How natural selection creates is shown with a simple example and clarified with two analogies, artistic creation and the "typing monkeys," with which it shares important similarities and differences. The creative power of natural selection arises from a distinctive interaction between chance and necessity, or between random and deterministic processes.

The third proposition is that teleological explanations are necessary in order to give a full account of the attributes of living organisms, whereas they are neither necessary nor appropriate in the explanation of natural inanimate phenomena. I give a definition of teleology and clarify the matter by distinguishing between internal and external teleology, and between bounded and unbounded teleology. The human eye, so obviously constituted for seeing but resulting from a natural process, is an example of internal (or natural) teleology. A knife has external (or artificial) teleology, because it has been purposefully designed by an external agent. The development of an egg into a chicken is an example of bounded (or necessary) teleology, whereas the evolutionary origin of the mammals is a case of unbounded (or contingent) teleology, because there was nothing in the make up of the first living cells that necessitated the eventual appearance of mammals.

I conclude that Darwin's theory of evolution and explanation of design does not include or exclude considerations of divine action in the world any more than astronomy, geology, physics, or chemistry do.

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