Myth: Evolution is only a theory.
Fact: The occurrence of evolution is a fact; how it occurred is a theory.
Summary
Evolution is a fact in that scientists know beyond reasonable
doubt that it happened. The exact mechanism of evolution --
that is, exactly how it happened -- is still a theory.
Argument
Evolution is both a fact and a theory. Mainstream scientists
consider it a fact that evolution occurred; how
it occurred is still considered a theory. Stephen J. Gould describes
this difference best:
"In the American vernacular, 'theory' often means 'imperfect
fact' -- part of a hierarchy of confidence running downhill from
fact to theory to hypothesis to guess. Thus the power of the creationist
argument: evolution is 'only' a theory and intense debate now
rages about many aspects of the theory. If evolution is worse
than a fact, and scientists can't even make up their minds about
the theory, then what confidence can we have in it? Indeed, President
Reagan echoed this argument before an evangelical group in Dallas
when he said (in what I devoutly hope was campaign rhetoric):
'Well, it is a theory. It is a scientific theory only, and it
has in recent years been challenged in the world of science --
that is, not believed in the scientific community to be as infallible
as it once was.'
"Well evolution is a theory. It is also a fact. And facts
and theories are different things, not rungs in a hierarchy of
increasing certainty. Facts are the world's data. Theories are
structures of ideas that explain and interpret facts. Facts don't
go away when scientists debate rival theories to explain them.
Einstein's theory of gravitation replaced Newton's in this century,
but apples didn't suspend themselves in midair, pending the outcome.
And humans evolved from ape-like ancestors whether they did so
by Darwin's proposed mechanism or by some other yet to be discovered.
"Moreover, 'fact' doesn't mean 'absolute certainty'; there
ain't no such animal in an exciting and complex world. The final
proofs of logic and mathematics flow deductively from stated premises
and achieve certainty only because they are NOT about the empirical
world. Evolutionists make no claim for perpetual truth, though
creationists often do (and then attack us falsely for a style
of argument that they themselves favor). In science 'fact' can
only mean 'confirmed to such a degree that it would be perverse
to withhold provisional consent'. I suppose that apples might
start to rise tomorrow, but the possibility does not merit equal
time in physics classrooms.
"Evolutionists have been very clear about this distinction
of fact and theory from the very beginning, if only because we
have always acknowledged how far we are from completely understanding
the mechanisms (theory) by which evolution (fact) occurred. Darwin
continually emphasized the difference between his two great and
separate accomplishments: establishing the fact of evolution,
and proposing a theory - natural selection -- to explain the mechanism
of evolution." (1)
Some nit-pickers might try to argue that nothing can ever be proven
100 percent in science, therefore there is no such thing as a
fact, let alone evolution standing as a fact. H.J. Muller tackles
this argument:
"The honest scientist, like the philosopher, will tell you
that nothing whatever can be or has been proved with fully 100%
certainty, not even that you or I exist, nor anyone except himself,
since he might be dreaming the whole thing. Thus there is no sharp
line between speculation, hypothesis, theory, principle, and fact,
but only a difference along a sliding scale, in the degree of
probability of the idea. When we say a thing is a fact, then,
we only mean that its probability is an extremely high one: so
high that we are not bothered by doubt about it and are ready
to act accordingly. Now in this use of the term fact, the only
proper one, evolution is a fact. For the evidence in favor of
it is as voluminous, diverse, and convincing as in the case of
any other well established fact of science concerning the existence
of things that cannot be directly seen, such as atoms, neutrons,
or solar gravitation...
"So enormous, ramifying, and consistent has the evidence
for evolution become that if anyone could now disprove it, I should
have my conception of the orderliness of the universe so shaken
as to lead me to doubt even my own existence. If you like, then,
I will grant you that in an absolute sense evolution is not a
fact, or rather, that it is no more a fact than that you are hearing
or reading these words." (2)
Return to Overview
Endnotes:
1. Stephen J. Gould, "Evolution as Fact and Theory,"
Discover, May 1981. Both quotations have been taken from
Larry Moran's FAQ,
"Evolution is a Fact and a Theory," which addresses
this issue in much greater detail.
2. H. J. Muller, "One Hundred Years Without Darwin Are Enough"
School Science and Mathematics 59, (1959) pp. 304-305.
Reprinted in Evolution versus Creationism, J. Peter Zetterberg,
ed., (ORYX Press, Phoenix AZ 1983).