Positivism vs Realism

Tom DiBenedetto tdib at UMICH.EDU
Mon Dec 15 06:17:15 CST 1997

James Francis Lyons-Weiler wrote:

tdib sez:
>> We do not begin with any hypotheses of convergence. They are a
>> result we are forced to accept when we encounter incongruence.

>       I never quite understand how a scientific inference leads
>       one to be forced to accept anything, if it's Popperian...

accept falsification,,,,,,then there is a need for alternative

>> There are no convergences to be corroborated before the test is run.

>       They either exist, or they do not.

sheeeesh,,,ok, to be precise, there are no hypotheses of convergence
to be corroborated before the test is run........
>> >       Popper and Miller's proofs in the early '80s show clearly
>> >       that when a test only serves to restate the obvious, (1)
>> >       no corroboration results,

>> and you think that a specific phylogenetic hypothesis is ever
>> obvious?

>       Sure- taxon a is the sister taxon to B, to exclusion of
>       all other taxa...

and this is obvious,,,eh? given only background knowledge??? maybe
you can help me with my dissertation!

>> >        (2) the test was not a critical test,

>> given the number that are falsified, how can you claim the test isnt
>> critical?

>       Apparently falsified!  And again, you are offering an
>       inductive justification - hardly Popperian.

huh? it is an inductive justification, incompatable with Popper, to
admit that a hypothesis is falsified by a test????????????

>> >       (3) time is better spent either thinking of new and
>> >       bold hypotheses or devising more critical tests that
>> >       surpass the no longer salient ones in their revelations.

>> so let me hear your bold hypothesis for the data of character
>> distribution......

>       OK- Ho.  There will be no significance difference between
>       the degree of implied nestedness in data set A and that
>       which may be expected by chance alone...

wow, you are a bold guy James. Unfortunatly I am doing systematics. I
meant to ask you for another bold hypothesis to explain character
distribution, maybe even with the goal of arriving at a tree. I didnt
really ask whether a pattern existed or not. I am not dismissing your
hypothesis. But I have ways of assessing whether there is much
corroboration for my nodes and my trees. I welcome yours as well. But
I dont see why you make a case against parsimony when your only
alternative addresses a different question.

>> Your significance test is not going to
>> yield a set of relationships. That is what we are after in
>> systematics, y'know....

>       Not just any set of proposed relationships - the
>       most accurate possible seems the goal...

fine, whether the most accurate possible is adjudged weak or strong
by your criterea is a separate matter. Or does your series of tests
ever indicate a preference for a less-than parsimonious tree?

>> ???? If data cannot be explained by the tested hypothesis, then we
>> need a new (smaller scale) explanation to account for it. This is not
>> in any way non-Popperian.

>       I disagree - it is completely ad-hoc.

OBVIOUSLY! Sheeeeesh,,,,,How many times have I said that homoplasy is
AD-HOC, that it is explanations for particular instances of
incongruence, that is is a BAD THING that we try to MINIMIZE.  And it
is certainly consistent with everything Popper wrote that we try to
arrive at corroborated hypotheses which are minimally ad hoc.

********************from Popper:
>>         "a high probability is a dubious reward for saying very
>> little, or nothing. In other words, the rule 'Obtain high
>> probabilities' puts a premium on ad hoc hypotheses. All this presents
>> a most uninspiring picture of science- a picture, moreover, that does
>> not in the least resemble the original. Indeed, what makes the
>> original so inspiring is its boldness; its boldly conceived
>> hypotheses, boldly submitted to every kind of criticism - to every
>> refutaton we can think of, including the most severe tests....."
>>         "Since testability in its turn can be measured by the content
>> of the theory, and since content, in its turn, can be measured by the
>> absolute logical improbability of the theory, content and
>> improbability stand in the same close relation to degree of
>> corroboration as does testability itself."

>       The first quote does not equate boldness with testability-
>       it is more compatible with the following
>       " If hypothesis h is bold, the degree of corroboration
>       is higher than if it had had a high logical probability.
>       Of course, this would require that h be testable..."

To rephrase you: if the hypothesis is bold, then the degree of
corroboration is higher than if it were ad hoc. Now your point seems
to be that being bold doesnt necessaily imply greater testability.
But the first quote directly links ad hocs with high probability,and
saying nothing....and presents a contrasting view of science based on
bold statements. To me, this implies directly a link between boldness
improbability, and saying something; and the second quote relates
this then to corroborability or testability.

>       Your use of the second quote is of interest, because
>       it reveals you confusion between "corroboration" and
>       "corroborability".  The statement, reworded with
>       proper predicates, is

>       Testability is linked to the content and improbility
>       (boldness) of a hypothesis.

Well thank you. We can stop right there. You have just admitted that
boldness is linked to testability (which is the same as

>        Since the content
>       of a hypothesis determines its testability, and
>       the content (amount of information we stand to
>       aqauire if the hypothesis survives the test)
>       determines the boldness of the hypothesis, content
>       and boldness are as important to the determination
>       of the degree of corroboration of the hypothesis
>       should it in fact survive the test.

....let us break down your reasoning.
1. since the content....determines TESTABILITY
2. and content .....determines BOLDNESS
3. content and boldness are as important to the determination of the
DEGREE OF CORROBORATION should it survive the test.

Now I am not saying this is wrong, because I think Testability and
degree of corroboration are linked,,,,but you are using this analysis
to argue to me that I am confused becuase I would go from step 1. and
step 2. to then say
3. Boldness is linked to testability through content.

Let us recall that this exchange derived from this statement of
>       ...... bold hypotheses need not be
>       testable - no definition of boldness is tied to
>       falsifiability.

I think you demonstrate very well that boldness and testability are
linked, and thus to falsifiability, and corroborability.

>       Boldness and degree of falsification achieved may be
>       linked, and bold hypotheses may be easier to test -

yes,hence testable. or falsifiable, or corroborable

>       but falsification itself does not demand boldness.


>> Boldness clearly relates to hypotheses which are improbable on the
>> background knowledge alone; they are the opposite of ad hoc
>> hypotheses which say very little.

>       No - you're wrong here.  Ad-hoc hypotheses may be bold;
>       in fact all hypotheses (ad-hoc or not) have some inherent
>       degree of boldness.  It's a lost cause to claim that
>       ad-hoc hypotheses and bold hypotheses are antitheses.

Well lets see what ol' Pop says about that"
        "But it is well known that ad hoc hypotheses are disliked by
scientists; they are, at best, stop-gaps, not real aims. (Scientists
prefer a bold hypothesis because it can be more severely tested, and
independently tested). (Conjectures and Refutations, p.287)

This seems to argue convincingly against your assertion that it is a
lost cause to contrast ad hocs and bold hypotheses,,,and it also
directly contradicts your statements that bold hypotheses are not
inherently highly corroborable (testable).

>> degree of corroboration, C(h,e,b)= p(e,hb)-p(e,b) should enable you
>> to see this. (The denominator is merely a normalizing factor)
>> This can be related to parsimony as follows:
>>         "It can be shown that what is usually called the simplicity
>> of a theory is associated with its logical improbability.....This
>> indeed, allows us to deduce,....why it is always advantageous to try
>> the simplest theories first. They are those which offer us the best
>> chance to submit them to severe tests; the simpler theory has always
>> a higher degree of testability than the more complicated one."

>       that only means they are easier to test - not that they
>       are magically better corroborated than more complex
>       tests that have also survived a critical test.

they have a higher degree of testability as well as being easier to
test. Obviously this doesnt mean they are magically better
corroborated,,hell, they can be falsified! But if they pass the test,
then they are more corroborated because the degree of corroboration
is a function of the probability of the evidence relative to
background knowledge AND the hypothesis, minus relative to background
knowledge alone (see the formula above - I'm sure you are capable of
understanding it). Boldness refers directly to just this - the
content of the hypothesis, i.e. the extent to which the hypothesis
attempts to say something more than background knoweldge.
>>Alternative explanations for parts of the
>> data are taken up as necessary in light of the results of the test. I
>> dont see how this research program can be ignored unless you are
>> willing to deny the notion of descent as a factor which can order
>> homologies in a hierarchial manner.
>       I am willing to not deny it - but I am not willing to deny
>       much else that could have occured, either - the more
>       complex possible pasts that envelope and include
>       simple hierarchical sorting of characters.

but that is not denied - that is homoplasy. Cladistics does not deny
homoplasy, rather we seek it out. But we do so by isolating that data
which cannot be explained by the higher level hypothesis (descent).
Reread the quote I gave you from Popper about the preference for the
simple explanation.

>       In not
>       allowing for the corroboration of hypotheses of convergence,
>       the parsimony "test" lacks imagination.

huh? If you want to propose a hypothesis of convergence when your
data is consistent with a hypothesis of descent, then you are engaged
in a whole different game than systematics as we have come to know
and love it. I suppose that the next thing you will come up with is a
hypothesis that aliens are riding around on our shoulders to keep us
in contact with the earth, rather than ascribing that to such a
unbold hypothesis as gravity.

>> >       Some bold hypotheses can be ad-hoc,

>> No. Ad hoc hypotheses are inherintly unbold. They account for
>> specific phenomena and say nothing beyond that. Boldness refers to
>> the scope of explanation that a hypothesis attempts.

>       OK - let's stop restating our position and get down
>       to contrived examples.

>       My hypothesis is whether or not pigs fly.

First off, that is not a hypothesis, it is a question. As stated it
is a bit like "All swans are white or not white". You think that is
a hypothesis?

>       So, I go about,
>       and I'm real good about, and check out plenty of pigs -
>       and I see none that fly.  I may even go so far as to
>       examine the repetoire of every pig on the planet.
>       If I want an ad-hoc hypothesis, I only need to say that
>       pigs fly under circumstances that prevent us from
>       detecting them.  this is a low-content, untestable
>       ad-hoc hypothesis that saves my hypothesis (to no one's
>       satisfaction, I hope).

First of all, what was your hypothesis, the one that needed saving??
(I guess it is that pigs DO fly - but that is not what you said).
Second, your saving hypothesis is NOT an ad hoc hypothesis. It is low
content alright, it is untestable alright, and it certainly wouldnt
satisfy anyone, but it is not ad hoc. As Popper uses the term "...the
unacceptable rule; always use the theory which is the most ad hoc,
i.e. which transcends the available evidence as little as possible"
(ibid. p.61).
        An ad hoc hypothesis addresses the evidence, and tries to say
very little if anything more. Popper discusses this at length in his
critique of induction -  the point being that inductive inferences do
just that - explain the data at hand and very little more. Your
attempt to save
your original hypothesis extends well beyond the data at hand, and
postualtes something new and totally unexpected. It would be a bold
hypothesis if it didnt contain the seeds of its own untestablilty. It
ends up as simply a unscientific statement.

>       Now for an example of an ad-hoc hypothesis that is
>       not bold.

no use wasting space here,,,,no ad hoc is bold. Your example works

>       If I hypothesized that aliens manipulated the species'
>       occurences, now that's a bold ad-hoc hypothesis.

No James, it is oulandish, not bold. Popper uses the term boldness in
a precise manner to refer to hypotheses which have great generality,
great CONTENT, and thus great testability. They are bold because they
seek to explain A LOT. Your alien hypothesis has none of those

>> Bold hypotheses are bold because they have high information
>> content.

>       The information content of a hypothesis is one term
>       you seem to consistenly misuse.  It is the amount of
>       new knowledge that would be aquired if the test is passed -
>       i.e., the information content is the potential consequences
>       of the hypothesis.

NO. As Pop says:
"..if we are interested in bold conjectures, even if...false, then
this interest is due to our methodological conviction that only with
the help of such bold conjectures can we hope to discover interesting
and relevant truth. ....Interest or relevance, in the sense here
intended can be objectivly analyzed..it depends on the explanatory
power, and thus on the content or improbability of the
informatin."(ibid. ch. 10)
"...the corroborability of a statement - its highest possible degree
of corroboration - equals its content" (ibid. p.288 - note: I
substituted corrroboration  for the original confirmation - Popper
elsewhere explains why he moved to use the new term, without any
intent to change the meaning).

Content is defined in terms of testabiltiy, corroborability. Boldness
also refers to content-  statements are bold to the extent that they
say a lot (are as far as possible from ad hoc)_and are thus open to a
lot of testing.

>> boldness and testability are inherintly linked.

>       No, boldness and degree of corroboration are linked
>       NOT corroborability!!!

wrong buddy.,,,,the reason we call a hypothesis bold is because of
the vulnerability to testing that is inherent in it. That is
testability, corrroborability. These in turn can be linked to the
degreee of corroboration, once the tests are made.

>> You are
>> intent on making a judgement as to whether that degree [of corroboration] is
>> significant. That is a different question. Whether it is or isnt
>> significant by your criterea, the results are not to be ignored in
>> favor of a less corroborated hypothesis.

>       Your conclusion is a non-sequitur; so even when there is
>       no remarkable congruence, you're going to talk about it
>       anyway? (Remarkable in the Popperian sense).

you mean remarkable in a Lyons-Weiler sense! - its your test, based
on your theory, or do you  mean to claim that RASA=truth?

>        In face of
>       the results of a test that have dismissed the hypothesis
>       of siganificant congruence, you're going to press on
>       and summarize what amounts to noise?

dismissed by your standards, that is (and of couse MY data is not
dismissed by
that). Tell me, have you sampled published morphological datasets to
determine what percentage are reporting insignificant conguence, by
your standard? I would be very interested to know the results of

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