John:>>>I wrote in the autevolution paper on the problem with metaphore. Yes,
>>>everything may be metaphorical at some level, but we do make a distinction
>>>between the epistemology of science and more colloquial metaphores.
>>
Alexei:>>This distinction is quantitative, not qualitative.
>
John:>I don't understand this comment. The distinction in epistemology is
>"mechanism" (which is an unfortunate term now that we are discovering a
>non-mechanical reality). Metaphores are statements of similarity without
>any proposed means for explaining the "cause" of that similarity. There's
>no need to get too esoteric about "mechanism" and "cause" here because
>there are plenty of simple examples. Darwin proposed "survival of the
>fittest" (reluctantly adopting these words, actually) as a metaphore, and
>said so. After the "modern synthesis," which provided the "mechanism" for
>evolution it was no longer considered a metaphore.
This is an important issue because it draws a line between realists (John)
and pragmatists (me). Realists say that metaphors imitate reality
wheras models represent reality (capture "causes" and "mechanisms"). This
view in well supported by scientific practice where we can see both
phenomenological metaphors (or "instrumental models") and mechanistic
models that attempt to represent real proscesses. Although I agree that
these categories of models exist, I don't see a qualitative difference
between them. The only difference is in the number of hierarchical levels
they try to represent. Phenomenological models do not go beyond 1 level
(i.e., the surface), and mechanistic models go deeper, representing
2, 3, or more hierarchical levels. Different phenomena tend to have
common deep hierarchical layers. Thus mechanistic models are more
integrated with each other, whereas phenomenological (instrumental)
models do not form a system. Mechanistic models are more stable historically
because they form a coherent system. It is like a crossword puzzle:
the more intersection of words you have, the smaller is the number
of ways to fill the puzzle. But there is no guarantee that the solution
of the puzzle that you have found is the only possible solution. May be
it is the only possible solution for the current English language (as
it is represented by Webster dictionary), but languages evolve, and it
may happen that in the future we will get a second solution for the same
crossword puzzle.
In practice we think that probable and improbable things are qualitatively
different. But if we consider probabilities, then p=1.0 and
p=0.00000000000000001 differ only quantitatively, and there may be
intermediate cases.
>Here's how I would write the story: The Ptolemean system was an excellent
>example of an instrumental model. It did not propose a "mechanism" but was
>rather based on the presumed symmetry of nature (the going concept of God
>at the time) and so was constructed on the geometry of circles (because God
>is perfect). When the reality of its mechanism is questioned, it becomes
>untestible as an explanation of the solar system, but it is a perfectly
>good model up to a given precision. Ptolemy wasn't trying to explain it, he
>was just trying to predict it, and show its harmony with his concept of
>God. Its something like investors might do today with trend analysis vs.
>looking at the fundamentals of a stock or commodity. Its failing was
>parsimony. Greater precision required increasing complication in the
>formulation. Newton's causally based approach was much more parsimonious
>because it provided a mechanistic approach to predicting the orbits. I
>would agree that Ptolemy's model, and all instrumental models, are
>metaphores of varying precision. But any attempt to produce a causal
>explanation and test it empirically is a qualitatively different kind of
>excercise, and in the language of epistemology, it is distinguished from a
>metaphore.
Actually, Ptolemean system was much deeper than an "instrumental model".
It included several deep levels, e.g. theology which at that time was
considered as fundamental as now we consider the atomic structure of
the world. It was simply the best solution of the crossword puzzle
available at that time. Now we have a better solution, but who knows,
may be future generations will find something even better and will laugh
at us and call us "instrumentalists".
-Alexei
-------------------------------------------------
Alexei Sharov Research Scientist
Dept. of Entomology, Virginia Tech, Blacksburg, VA 24061
Tel. (540) 231-7316; FAX (540) 231-9131; e-mail sharov@vt.edu
Home page: http://www.gypsymoth.ento.vt.edu/~sharov/alexei.html