Sunday, January 22, 2017


One of advantages of writing essays for my blog has been that the discipline forces me to test my points of view and, if necessary, modify or at least refine them.  This essay represents one such refinement.  In past references to evolution, I have often avoided using the term “theory” on the assumption that the principles of evolution are much too firmly established to relegate them to what might be considered “just a theory.”  Upon further reflection, I have decided that there is nothing wrong with referring to evolution as a theory.

In everyday parlance the term theory can mean something as simple as a hunch:  My theory is that “Professor Plum did it with a lead pipe in the billiard room,” or “Betty is physically attracted to Walter.”  But in science the term “theory” has come to mean something very different from a mere guess.  The OED defines a scientific theory as a statement of general laws, principles, or causes of something known or observed.  Thus we speak of a “theory of gravity,” a “theory of relativity,” or a “theory of plate tectonics.”

To qualify as a scientific theory, there must be a set of statements (a) that are intended to explain facts about the real world, (b) that are consistent with the known facts, and, most importantly, (c) that make hypotheses that are subject to confirmation or disconfirmation through further observation and experimentation.  In those important senses, a scientific theory is not “merely” a theory.

One further point:  If a scientific theory has been tested repeatedly and its major points confirmed over and over, at some point we refer to it as “scientific fact.”  That doesn’t mean that such a fact will not be disconfirmed at some point in the future.  All scientific facts (or scientific truths, if you will) are held tentatively and subject to disconfirmation.  For literally centuries, Newton’s theory of gravity was tested and confirmed and accepted as scientific fact, only to be superseded by the theory of relativity.  In a sense, the term “scientific fact” is simply a shorthand for a principle that has been repeatedly tested and confirmed but that necessarily remains tentative.

Based on the above understanding, evolution clearly qualifies as a scientific theory.  Moreover, its repeated testing and confirmation have elevated it to the status of scientific fact.

© 2017 John M. Phillips

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