Re: Popper's 'Scientific' Irrationalism

Lee Daniel Crocker (
Wed, 19 Mar 1997 17:50:43 -0800 (PST)

LDC: <This is insufferable misinterpretation
of Popper, and with no excuse given other than Stove's own emotional
discomfort with carefully reasoned ideas.... Mr. Stove seems uncomfortable
with the obvious fact that expanding knowledge implies expanding
ignorance.... Mr. Stove's discomfort with "conjectural knowledge" is
merely cowardice: he doesn't want to admit that every act taken by every
human being is a gamble on the efficacy of what we call knowledge. He
seems dismayed by that rather than enlivened and freed. That's /his/
failure, not Popper's.>

>RJ: Oh my. Armchair pschoanalytical attributions of emotional defects to
>other individuals' reasoning processes does not make those reasoning
>processes irrational. The armchair stance itself is irrational; it is not
>reasoning, it is political invective. Popper's "carefully reasoned ideas,"
>as you put it, were in fact, sloppily executed attempts to unsuccessfully
>deduce his way out of a wet paper bag. See the fatal critique below.

And those last two senteces are clean epistemology? I indulged in a bit
of psychologizing precisely because Stove's rhetoric deserved no better.
Your "fatal critique" is also riddled with content-free connotations and
hidden implications. At least I was honest enough to use "seems" in my
rhetoric: Stove seems to take himself seriously. Nonetheless, if you
and others might be taken in by him, I suppose a more careful analysis
of his mistakes might be useful, so I'll attempt it here.

> "Popper's criterion of falsifiability requires that we be able to single
> out a special class of sentences and call them observation sentences. A
> proposition is then said to be falsifiable precisely when it is related to
> observation sentences in a special way: Proposition P is falsifiable if
> and only if P deductively implies at least one observation sentence O. One
> problem with Popper's proposal is that it requires that the distinction
> between observation statements and other statements be made precise. To
> check the statement 'The chicken is dead,' you must know what a chicken is
> and what death is. *This problem is sometimes expressed by saying that
> observation is theory laden.* Every claim that people make about what
> they observe depends for its justification on their possessing prior
> information. Popper addresses this problem by saying that what one regards
> as an observation statement is a matter of convention. But this solution
> will hardly help one tell, in a problematic case, whether a statement is
> falsifiable. For Popper's criterion to have some bite, there must be a
> nonarbitrary way to distinguish observation sentences from the rest. To
> date, no one has managed to do this in a satisfactory manner.

That's true, but to mistake "lack of adequate, precise explanation" of a
phenomenon (such as "observation") for the non-existence of the phenomenon
is exactly the justificationist mistake that critical rationalism avoids.
Observation exists; to deny that is an inexcusable evasion of reality.
You might as well say that we don't have a precise definition of life, so
we cannot reason from the existence of life as a premise. Popper gave
an epistemological method for using observation to falsify propositions.
Since observation is the foundation of other epistemologies as well, you
must criticise not observation itself, but his method of using it compared
to theirs. If it is irrational to use observation to falsify, then it is
just as irrational to use observation to verify or justify.

> The problems with Popper's falsifiability criterion go deeper. First,
> there is the so-called tacking problem. Suppose that some proposition S is
> falsifiable. It immediately follows that the conjunction of S and any
> other proposition N is falsifiable as well. That is, if S makes
> predictions that can be checked observationally, so does the conjunction S
> & N. This is an embarrassment to Popper's proposal since he wanted that
> proposal to separate nonscientific propositions N from properly scientific
> propositions S. Presumably, if N is not scientifically respectable,
> neither is S & N. The falsifiability criterion does not obey this
> plausible requirement.

This plausibility exists only in your mind, not mine (nor, presumably,
Popper's). Sometimes it is not obvious that a statement is a conjunction
of two propositions; that is a feature of the ambiguity of language. The
act of pointing out such a mistake is good science. If years of study
have provided observations that failed to falsify S&N, then when someone
later expresses that proposition as actually a conjunction of two, that
new definition will serve to determine which of all those observations
might have falsified either S or N. If none would have falsified N by
itself, then its former alliance with (or rather parasitism on) S is no
reason to grant it any respectability it didn't earn on its own merit.
Darwin's Lamarckism is a good example. Before Lamarckism was largely
refuted, his theories contained it. Are we to then grant it unwarranted
respectability, simply because Darwin's observations once supported it?
No, we must reinterpret those observations as they serve the two
propositions seperately. Since none of his observations might have
falsified Lamarckism (because he didn't try), they do not support it.

> Another problem with Popper's proposal is that it has peculiar
> implications about the relation of a proposition to its negation. Consider
> a statement of the form 'All As are B.' Popper judges this statement
> falsifiable since it would be falsified by observing a single A that fails
> to be B. But now consider the negation of the generalization-the statement
> that say 'There exists an object that is both A and not-B.' This statement
> is not falsifiable; no single observed object or finite collection of them
> can falsify this existence claim. So the generalization is falsifiable,
> though its negation is not. But this is very odd-presumably, if a
> statement is 'scientific,' so is its negation. *This suggests that
> falsifiability is not a good criterion for being scientific.*

Statements--propositions--are neither scientific nor unscientific; it
is the epistemological method used to judge them that is evaluated
in those terms. But this is sometimes confusing--and Popper himself
is guilty of confusing language in this regard (or perhaps we can
blame his translators)--because we fail to see sometimes that our
choice of how to express a proposition implies in our minds the
epistemological method appropriate to test it. So when Popper says
that P is a more scientific statement than ~P, what he really means
is that the method implied for testing proposition P, expressed in
that form, is superior to the method implied by expressing it in the
form of ~P.

A proposition and its negation are just two points of view on the
same semantic relationship, but the definitions of entities in the
relation creates fundamental assymetries in measuring verisimilitude.
Take the definition of "A"; it is a set of rules for partitioning all
of entity-space into "A" and "non-A". Since entity-space is infinite,
we expect the cardinality of set {A} to be less than that of {non-A}.
Threfore, when we postulate a relationship such as "all A's are B",
any observations we make of non-A entities do not increase knowledge
much because they represent such an infinitesimal sample of {non-A}.
Observations of A's, on the other hand, increase verisimilitude by a
greater amount, because each A is a much larger sample of {A} than
each non-A is of {non-A}. Thus, in general, we may call observations
of {A} more scientific than observations of {non-A}, because they are
more likely to raise the virisimilitude of the proposition.

So, the statements "All A's are B" and "There exists an A that is not
B" are equivalent (but opposite) statements, and equally scientific.
But the method implied by stating it the first way, namely, "Attempt
to falsify by looking for A's that are not B", is the superior
scientific method to any method looking at all existents as implied by
the latter statement, becase it is more likely to be falsified.

> Still another problem with Popper's proposal is that most theoretical
> statements in science do not, all by themselves, make predictions about
> what can be checked observationally. Theories make testable predictions
> only when they are conjoined with auxiliary assumptions. Typically, T does
> not deductively imply O; rather, it is T & A that deductively implies O
> (here, T is a theory, O is an observation statement, and A is a set of
> auxiliary assumptions). This idea is sometimes called Duhem's Thesis...

And your point is? Really, I don't understand what you think is a problem
here. You already use the weasel-word "most" to admit that some statements
do imply falsifiable observations by themselves, but even supposing that
they required an additional assumption to test, can't you then judge the
value of the observation based on the falsifiability of the assumption?
If you accept the assumption as an axiom, then the observation tests the
original proposition; if you later falsify the assumption, then the test
no longer bears on the proposition, and you will have to find either a
better assumption or a way to test the proposition directly.

> The final problem with Popper's proposal is that it entails that
> probability statements in science are unfalsifiable. Consider the
> statement that a coin is fair-that its probability of landing heads when
> tossed is 0.5. ...It is possible for a fair coin to land heads on all ten
> tosses, to land heads on nine and tails on one, and so on. Probability
> statements are not falsifiable in Popper's sense. In fact, something like
> the Likelihood Principle is what Popper himself adopted when he recognized
> that probability statements are not falsifiable.

And your point is? Again, I don't see your problem here. Probabilities
in, probabilities out. Mathematicians deal well with this, why can't

> [Assymetry, conjunction, etc.]

This is just a repeat of arguments dealt with above, so I'll skip it.

> One problem with Popper's asymmetry thesis is that it equates what can be
> known with what can be deduced validly from observation statements.
> However, science often makes use of nondeductive argumentation, in which
> the conclusion is said to be rendered plausible or to be well supported by
> the premisses. In such arguments, the premisses do not absolutely
> guarantee that the conclusion must be true.

I don't think Popper would disagree with any of that; in fact, I don't
see any conflict at all. Such "generally accepted" inductive arguments
can be pragmatic, but that doesn't raise them to the level of scientific
until you can demonstrate falsifiability. "Plausible" just means they
might be worth the effort to try to falsify. Since there are likely to
be hundreds of such generally accepted ideas at any one time, how might
you choose which ones to invest research in? Simple: which ones are
likely to be the cheapest to falsify? That doesn't prevent you from
holding others as assumptions if you like them for esthetic reasons or
whatever. It just gives a more solid reason for choosing research.

> On the face of it, vulnerability appears to be a defect, not a virtue.

Then it's a good thing we and Popper look deeper than the face of it.

> Why is it desirable that the hypotheses we believe should be refutable?
> Wouldn't science be more secure if it were invulnerable to empirical
> disconfirmation?

It might be, but reality didn't give us that world. It gave us the
one with senses and cognition the way they are, not the one with God's
plan written in big letters on the sky.

> The Likelihood Principle helps answer these questions. The consequence
> of this principle is that if O favors H1 over H2, then not-O would favor
> H2 over H1. This is because if P(O/H1) > P(O/H2), then P(not-O/H1) <
> P(not-O/H2) [Original had H1 here; assuming it was a typo]. We want our
> beliefs to be supported by observational evidence. For this to be possible,
> they must be vulnerable; there must be possible observations that would
> count against them. This requirement is not a vestige of the discredited
> falsifiability criterion. It flows from the Likelihood Principle itself."

In other words "Here is Popper's falsifiability criterion, expressed in
more optimistic-sounding justificationist language so I can call it my
own original idea, and call Popper's 'discredited' for an additional
gratuitous insult." This principle as you describe it really is just
Popper's falsifiability from a different point of view. It is almost
precisely Popper's equations desribing verisimilitude.

Lee Daniel Crocker <>