[lit-ideas] Re: The Educational Value of Slips of the Whatever

Donal wrote (some time ago now)
More philosophically fundamental is P’s point that “winning” or the degree of acceptance of an argument are [historical] _facts_, and from these facts we cannot _deduce_ the _validity_ of what argument is “winning”. We may guess, one way or another, but we cannot _deduce_. This is enough to show there is a logical gap between “winning” and “validity”.
If winning means 'acceptance,' I'd have thought that the history of ideas from Aristotle's celestial mechanics to the acceptance of phlogiston as necessary for combustion would have shown this. That people accept and propose invalid arguments isn't really news.
When assessing “validity” we look for critical grounds, for what actually ‘supports’ (non-inductively, of course) the argument or theory under consideration. The answer is that whether an argument is genuinely valid is always a guess of some sort. Even if some of these guesses seem incontestable, the history of ideas is littered with the supposedly incontestable that was then overturned, and, perhaps more important philosophically, logically these guesses cannot be demonstrated – even deduction itself, surely that most sound of guesses, cannot be deduced deductively without the argument being fatally circular.
If for some, deciding whether an argument is valid amounts to a guess, a hunch, or a wild surmise, this would be an interesting fact about those who proceed this way, not about how validity is determined. I don't know what 'deduction itself' is supposed to mean: although validity is predicated of deductive arguments in 'formal' logic, validity itself is a simple notion that applies everywhere. An argument is valid if and only if its premises could not jointly be true and its conclusion false. 'Even if your premises were true, I wouldn't have to accept your conclusion.' I've never heard of the notion of validity itself being question. The underpinnings of a formal system, the stopping places, cannot themselves be supported in the way that the particular deductive moves they themselves support are by them supported. But this doesn't mean there's some doubt as to whether arguments of the form 'if p, then q, p, therefore q,' are valid or not.
What happens when we worry about what lies behind the axioms of a system is illustrated by Lewis Carroll's 'What the Tortoise said to Achilles' 

http://www.mathacademy.com/pr/prime/articles/carroll/index.asp
In truth we may often accept an argument _because it is valid_, but it would be wrong to conclude that because we accept it the argument therefore is valid. 

Right. Was Richard questioning this?

Richard himself now appears appears
Perhaps valid arguments may be proposed for questions like "Is it better to get up early or late in the morning?" Popper, I assume, however, is more interested in questions of fact like "Is the universe expanding?" And for that there are good and less good arguments, but no "valid" arguments. The validity of arguments about facts can only be judged by Laplace's Demon or a similarly omniscient entity.
Laplace's Demon is invoked to support one simple-minded version of determinism: suppose that such a demon knew everything (whatever that might mean) about the past and present states of the universe. The supposition is that such an omniscient creature would then be able to predict all of its future states. This creature's knowledge would help it to construct sound arguments, not merely 'valid' ones about 'facts,' and surely its the soundness of arguments that's here being confused with validity. A sound argument is a valid argument whose premises are true (however their truth is determined), and surely such truth-supporting facts are essential to determining whether an argument in, say, physics (where 'arguments' are perhaps more rightly called explanations). Validity all by itself is not enough.
P would agree, I think, with this last sentence provided we understand “judged” to mean “conclusively judged”. But we can, and do, make provisional judgments about such facts. Even whether "Is it better to get up early or late in the morning?". This question too, insofar as we treat it as a question fact, cannot be conclusively but only provisionally judged. Even where there are only "good and less good arguments" [getting-up-early being a case in point; science in general and metaphysics in particular being even more crucial cases] we may still speak of validity, and even make judgments as to validity, albeit in a non-conclusive sense.
Yes; but this doesn't mean that validity is problematic independently of the factual claims that make up a putative valid argument. There's some confusion about this throughout Donal and Richard's interesting exchange. I hope I've added to it. 

Robert Paul
The Reed Institute
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