More on realism
bryo at COMMTECH.NET
Wed Dec 10 11:19:50 CST 1997
> On Tue, 9 Dec 1997 08:57:10 -0800, Richard Zander wrote:
> >There are two approaches to viewing hypotheses and theories, realism and
> >anti-realism. These are much the same, since the first posits a reality,
> >then says it is correctable,
> what does that mean,,,,correctable?
Corrigible. A realist believes in a reality based on all the facts at
one's disposal, then changes the concept when more facts appear and make
> > and the second has all the trappings of the first, but denys the reality (acting "as >if").
> What exactly are you denying the reality of? Taxa, homologies,
> organisms? What, if anything, is real? Quarks?
Let's look at it this way. Maybe there there is a huge aggolmeration of
real things we observationally share to a greater or lesser extent and a
bunch we don't even know about. No matter. We can agree on what works,
pragmatically, and on what can be used (instrumentalism) be it ideas or
material things, to effect changes in our lives. We can ignore each
other's ideas of reality or even non-reality as long as joint tasks are
agreeable. We jointly aim at a classification of organisms that
facilitates prediction. To the extent, however, that philosophical
realists among cladists claim to have approached truth more closely than
I think they have approached truth (with a view to furthering a joint
effort), I complain.
> >They are both liable to
> >generating statistical nonsense. Realism, however, in positing the
> >reality of patterns, species, synapomorphies, opens the door to low
> >standards of hypothesis construction.
> I dont think your standards are any higher simply because you imagine
> that you can calculate a probability for something.
Sure they are.
> >Because realists feel that there
> >is a truth and that data converge to the truth, hypotheses that maximize
> >explanation or minimize falisification are presented as "approximately
> >the truth" even with they are of low probability.
> Low probability according to what? You keep repeating that as if it
> were some holy grail. There is no calculation of probability relative
> to truth; only to theory. So what if a minimally falsified hypothesis
All sentences are theory-laden. I call for an INDEPENDENT TEST OF
PREDICTIVE VALUE OF PHYLOGENETIC HYPOTHESES such that predictability of
the trees obtained is compared and evaluated in such a way that we can
feel the work is worthwhile. I predict that fine structure of trees from
both maximum parsimony and maximum likelihood analysis will not be worth
much as far as prediction goes.
> is adjudged to have low probability in light of some theory,,why does
> this indicate that it is false? Maybe the theory underlying the
> probability calculation is false.
Maybe so. In fact, I'm surprized that both cladists and statistical
phylogeneticists don't shuffle their feet and look ashamed more often.
> > Yes, the correct hypothesis (if it could be determined with a time
> >machine) is one of the hypotheses of low probability, but it is the
> >ability to choose which low probability hypothesis is the true one that
> >is the problem. Maximizing synapomorphies and maximizing likelihood only
> >narrows the field by eliminating grossly unreasonable trees.
> How can you say that? By what procedure do they eliminate only
> grossly unreasonable trees, but fail to eliminate all the rest,
> excepting one. Because you independently calculate a probability
> which indicates that a set of trees is "reasonable"? What if I were
> to say that your calculations are irrelevant or meaningless?
I call for an independent test of the predictive value of phylogenetic
hypotheses. This theorization is somewhat circular and solipsistic.
> > Thus, reification associated with realist attitudes introduces
> >idealist attitudes into realism, which is supposed to be its
> >philosophically exact opposite.
> I dont think there is any idealism involved. And it seems that you
> are the one who is engaged in some sort of a dance with the notion of
> truth. You seem to beleive that you can calculate the probability of
> something being TRUE. How can an anti-realist hold such a position?
Good retort. Answer is I think I can calculate the PROBABILITY of
something being true. Note emphasis. However, a big however, calculating
probabilities of things that happened ONCE in the PAST could be
laughable without the potential of molecular data from say a couple of
independent, selectively neutral genes. No you can't calculate
probabilities with morphological data, unfortunately.
> Tom DiBenedetto http://www-personal.umich.edu/~tdib/
> Fish Division tdib at umich.edu
> University of Michigan Museum of Zoology
Richard H. Zander, Buffalo Museum of Science
1020 Humboldt Pkwy, Buffalo, NY 14211 USA bryo at commtech.net
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