Thoughts in a Haystack

One frequent delusion of ID proponents asserts, implicitly or explicitly, that if evolution fails to explain some biological phenomenon, intelligent design must be the correct explanation. This is a misunderstanding of the scientific process. If one explanation fails, it does not necessarily follow that some other explanation is correct. Explanations must stand on their own evidence, not on the failure of their alternatives. Scientific explanations or hypotheses are creations of the mind, conjectures, imaginative exploits about the makeup and operations of the natural world. It is the imaginative preconception of what might be true in a particular case that guides observations and experiments designed to test whether the hypothesis is correct. The degree of acceptance of a hypothesis is related to the severity of the tests that it has passed.

The discovery of oxygen did not simply happen because it was shown that phlogiston does not exist. Nor is the periodic table of chemical elements accepted just because chemical substances react and yield a variety of components. Similarly, Darwin's theory of evolution by natural selection became generally accepted by scientists because it has sustained innumerable tests and has been fertile in yielding new knowledge. Other evolutionary theories, such as Lamarck's, have failed the tests of science. For a theory to be accepted, it is not sufficient for some alternative theory to have failed.

-Francisco J. Ayala, Darwin and Intelligent Design