Does the Theory
Lead to Testable Predictions?
Edward S. Deevey, Jr., "The Reply:
Letter from Birnam Wood," Yale Review, Vol. 61, 1967, p. 639.
...Unfortunately, for the same reason that happenings do not make good
theatre, existential experiments, the sort that might help to demonstrate post-Darwinian
evolution, are very hard to design. In fact, by canons promulgated in every textbook, they
would be bad experiments. The best ones--I do not say the only good ones, or the only
conceivable ones--are still those that nature set up so long ago. Which is why
evolutionists are still historians, not prophets.
Ernst Mayr, Science, Vol. 134, 10 Nov. 1961, p.
I doubt that there is a scientist who would question
the ultimate causality of all biological phenomena--that is, that a
causal explanation can be given for
past biological events. Yet such an explanation will often have to be so
unspecific and so purely formal that its explanatory value can certainly
be challenged. In dealing with a
complex system, an explanation can hardly be considered very illuminating
that states: "Phenomenon A is caused by a complex set of interacting factors, one of
which is B." Yet often this is about all one can say.
Ibid., p. 1504.
The theory of natural selection can describe and explain
phenomena with considerable precision, but it cannot make reliable
predictions, except through such
trivial and meaningless circular statements as, for instance: "the fitter individual
will on the average leave more offspring." Scriven has emphasized
quite correctly that one of the most important contributions to philosophy
made by the evolutionary theory
is that it has demonstrated the independence of explanation and prediction.
Stephen Tolumin, Foresight and Understanding
(Harper Torchbooks, New York, 1961), p. 24.
...[Historical theories] have led to no categorical verifiable forecasts
whatever. One obvious example is Darwin's theory, explaining the origin of species by
reference to variation and natural selection. No scientist has ever used this theory to
foretell the coming-into-existence of creatures of a novel species, still less verified
R.H. Peters, "Tautology in Evolution and
Ecology," American Naturalist, Vol. 110, Jan.-Feb. 1976, p. 1.
I argue that the `the theory of evolution' does not make predictions, so
far as ecology is concerned, but is instead a logical formula which can be used only to
classify empiricism's and to show the relationships which such a classification implies.
Similar criticisms are then made of several ecological concepts. The essence of the
argument is that these `theories' are actually tautologies and, as such, cannot make
empirically testable predictions. They are not scientific theories at all.
Ibid., p. 11.
Analysis of a number of popular ecological tenets, including natural
selection, competitive exclusion, and parts of succession, species diversity, and spatial
heterogeneity, reveals that they lack the predictive and operational qualities which
define scientific theories. Instead they consist of the logical elaboration of certain
axioms. Consequently, they must be termed tautologies.
Tautologies may be useful logical aids, but they cannot replace true
theories. Unless ecologists are careful to distinguish the two, their confusion may
produce a body of thought resting on metaphysical rather than empirical, predictive