Popper: Notes from the Front

[Philidor11@aol.com]

Good precept:  when you bump into your ignorance stop talking.

I've been doing some reading and here's something interesting:

<<He makes it clear that he had always distinguished between the purely 
logical sense of falsifiability (which defines his demarcation criterion) and 
the methodological impossibility of obtaining a definitive or conclusive 
falsification. The former is based on a logical relationship between the 
theory and basic statements (statements contradicting the theory and 
describing observable things). Each generation of students "discovers" that 
Popper's criterion is not applicable because one cannot conclusively refute 
any theory. But Popper's point was that we must decide in advance which 
states of affairs (basic statements) we would accept as refutations of our 
theory. If I claim that all swans are white, I must be able to describe at 
least one circumstance which contradicts the theory and under which I would 
abandon my claim. 

Look out for this travesty of Popper's analysis: "You cannot prove a theory, 
but you can disprove it". (This is important because even Popper, when 
speaking roughly of his method, used the word "disprove". See page 192 of 
Conjectures and Refutations.) This travesty allows superficial critics to say 
"but to disprove a theory is simply to prove its contradictory; and if we can 
prove then we can be certain, but Popper told us that we cannot eliminate 
uncertainty, and thus Popper fails to escape the problem of uncertainty." 

This common mistake confuses demonstration and derivation. Proof is a matter 
of demonstration (as in mathematics), but refutation is a matter of accepting 
a basic statement and rejecting the truth of the theory it contradicts. If I 
accept "This swan here is black", then I am obliged to reject "All swans are 
white". Because from "This swan here is black" I can derive "Not all swans 
are white". But I have not proved that not all swans are white, that this 
must be true. In a proof, we discard the assumptions that helped us to get to 
the conclusion. This is quite clear in proof by reductio ad absurdum. In a 
reductio ad absurdum we start by assuming the opposite of what we wish to 
prove. That is, we assume it is false. We then try to infer an absurdity 
(contradiction) from this, and if we do, we then conclude that the assumption 
must be true. But in a refutation our rejection of a theory ("All swans are 
white") depends on our maintaining the truth of the basic statement ("This 
swan here is black"). In a refutation we hold on to the assumptions of our 
derivation.>>
http://www.eeng.dcu.ie/~tkpw/intro_reading/
(this is a brief description of Karl Popper's Main Works in English) 

The observation of the black swan is subject to the same uncertainties as the 
observations of the white swans.  However, if we decide in advance that a 
black swan
observation with the same degree of acceptability as the white swan 
observations will constitute a refutation, then our hypothesis is in fact 
falsifiable.  (Wish this used the word hypothesis instead of theory, and, by 
the way, this adds another layer of arbitrariness.)
Problem:  so often when you thrash your own way through a logical jungle you 
find there's a cleared path just over there.  Still, I wouldn't have missed 
the thrashing.