First, is the 'survival of the fittest' principle actually a tautology?
A. The usual route to generating the alleged tautology is to combine
the
idea of the survival of the fittest with a definition of fitness in
terms of survival - so that the survivors are those that survive. But
that certainly is not everyone's definition
(even some critics - e.g. Henry Morris - employ concepts of fitness that
do not reduce to survival), and although survival is typically *linked*
to fitness, I do not know of any textbook that makes that a definitional
connection.
B. In any case, the 'survival of the fittest' principle is not the
whole of
evolutionary theory. (Survival of the fittest could be true even in the
complete absence of evolutionary movement - as Darwin himself
saw.) Anyway (as Brian noted) even if that part of evolutionary theory
*were* tautological, that would not show that the theory as a whole was.
Indeed, *any* non-tautological principle is trivially provably logically
equivalent to some larger principle, part of which will be tautological.
Second, suppose that the 'tautology' charge sticks. Exactly what would
that show?
C. Given that tautologies are necessarily
true, that would merely establish that the principle in question was
unassailably true - and *that* is hardly a criticism.
D. The usual charge is, however, that the principle (or theory) reduces
to
an *empty* tautology, and that that somehow damages its status as
scientifically substantive.
But it isn't that simple. I had planned to post something
concerning Newton and F = ma on this point, but Brian beat me to it.
However, I don't completely agree with everything he said here, so hope
everyone will indulge me for a couple more remarks on the topic.
It is a basic Newtonian principle (first law) that velocity of an object
remains
constant unless the object is subject to a force. Force is, of course,
quantified as ma (that's the substance of the second law), acceleration
being defined in terms of change in
velocity. The principle in question thus reduces to: velocity of an
object remains constant unless the object is subject to a change in
velocity. Well, *that's* hardly news. And in practice, how is it
determined that a force is being applied? A change in a vector. Uh oh.
That all looks about as empty and tautological as the 'survival of the
fittest' case. In fact, Holton (_Introduction to Concepts and Theories
in Physical Science_, 2e, p118, 119) terms all this a "vicious circle".
Does that count against Newtonian physics? No, says Brian - and I think
he's exactly right on that. But Brian's rescue of Newtonian physics
seems to rest on the claim that e.g., the first law is not a
*definition* of F, but, rather, that F, m, and a can be independently
determined, and when so determined, we simply discover that lo and
behold, the independent value of F is always identical to the product of
the independent values of m and a.
Well, (i) I don't believe that Brian is right here, and (ii) I don't
think that's how Newton got F=ma either. (Actually, "F = ma" never
shows up in the _Principia_ - see Holton.) I think that we are dealing
with a definition here - or at least an interdependent system of
definitions. And if so, then if the 'tautology' charge (even were it
correct) is damaging against Darwin, it would be equally damaging
against Newton.
So how can Newton be rescued here? One way (adopted by e.g. the
physicist Milton Rothman), is to admit that the entire Newtonion system
is simply a stipulative definition of "inertial system", then take the
empirical content of Newtonian physics to be simply the verification
that there are in fact inertial systems - maybe even nature as a whole.
Holton's way is to admit that 'inertia' and 'force' are defined in terms
of each other (the 'vicious circle'), but to hook the system up with
nature via the selection of some object as an 'essentially arbitrary .
. . standard of mass', then pegging everything else to that.
In any case, Brian said that
"For Newton's second law to have any significance it is necessary for
all three quantities (force, mass and acceleration) to be defined
independently of the law itself. Only then does Newton's law have any
force."
I'm curious as to how that is to be done - how those three can be
defined *independently* of each other (and also not mutually parasitic
on or reducible to some other stipulatively defined concept - e.g.
inertia).
Back to the main issue - natural selection and tautology. There may be
some difficulty for Darwin somewhere in the region here, but if there
is, the attempts to locate it in a tautology charge may not be quite on
target.
Del
Del Ratzsch voice: (616) 957-6415
Philosophy Department (616) 451-4301 (home)
Calvin College e-mail: dratzsch@legacy.calvin.edu
Grand Rapids, MI 49546 fax: (616) 957-8551