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Chance and Necessity

Natural selection accounts for the "design" of organisms, because adaptive variations tend to increase the probability of survival and reproduction of their carriers at the expense of maladaptive, or less adaptive, variations. The arguments of Aquinas or Paley against the incredible improbability of chance accounts of the origin of organisms are well taken as far as they go. But neither these scholars, nor any other authors before Darwin, were able to discern that there is a natural process (namely, natural selection) that is not random but rather is oriented and able to generate order or "create." The traits that organisms acquire in their evolutionary histories are not fortuitous but determined by their functional utility to the organisms.

Chance is, nevertheless, an integral part of the evolutionary process. The mutations that yield the hereditary variations available to natural selection arise at random, independently of whether they are beneficial or harmful to their carriers. But this random process (as well as others that come to play in the great theatre of life) is counteracted by natural selection, which preserves what is useful and eliminates the harmful. Without mutation, evolution could not happen because there would be no variations that could be differentially conveyed from one to another generation. But without natural selection, the mutation process would yield disorganization and extinction because most mutations are disadvantageous. Mutation and selection have jointly driven the marvelous process that starting from microscopic organisms has spurted orchids, birds, and humans.

The theory of evolution manifests chance and necessity jointly intricated in the stuff of life; randomness and determinism interlocked in a natural process that has spurted the most complex, diverse, and beautiful entities in the universe: the organisms that populate the earth, including humans who think and love, endowed with free will and creative powers, and able to analyze the process of evolution itself that brought them into existence. This is Darwin's fundamental discovery, that there is a process that is creative though not conscious. And this is the conceptual revolution that Darwin completed: that everything in nature, including the origin of living organisms, can be accounted for as the result of natural processes governed by natural laws. This is nothing if not a fundamental vision that has forever changed how humanity perceives itself and its place in the universe.

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Go to Evolution Topic Index

Chance and Necessity

Evolution: Topic Index
The Darwinian Revolution
Darwin's Discovery: Design without Designer
Natural Selection as a Directive Process
Natural Selection as a Creative Process
Natural Selection as an Opportunistic Process
Teleology and Teleological Explanations
The Compatiblity of Teological and Causal Explanations
Coda: Science as a Way of Knowing


Dr. Francisco Ayala
Dr. Francisco Ayala


See also:

The Relation of Science & Religion
Purpose and Design
The Argument From Design
The Anthropic Principle
Charles Darwin
Sir Isaac Newton
DNA Double-Helix