RE: SUO: RE: Peirce's "Questions Concerning Certain FacultiesClaimed for Man"
"Philip Jackson" <phil.jackson@computer.org>, replying to John Sowa:
Thanks very much for your reply.
You wrote:
>
> Some brief comments on your response to Jon A.
>
> >That is fine, and I appreciate your discussion of these terms in
> the context
>
> >of Peirce, Kant and Descartes.
> >
> >However, I am more concerned by Peirce's following statements which were
> >made in relatively plain English:
> >
> >"all knowledge of the internal world is derived by hypothetical reasoning
> >from our knowledge of external facts."
>
> An example of what Kant claimed and what Peirce denied
> is that our knowledge of space and time is not derivable
> from perception. P would say that everything we know about
> space and time is derivable from sensory input combined
> with abduction (hypothetical reasoning). He would classify
> "observation" of mental imagery and perception of pain,
> headache, toothache, etc., to be of the same nature as
> "external facts".
Thanks for this clarification. It seems unusual to define "external facts"
to include observation of mental imagery. However, if that is the case, then
it seems my question is answered affirmatively -- i.e., we can have some
knowledge of the "internal world" by direct observation of our thoughts (or
at least, direct observation of our self-verbalization of our thoughts).
This area is a philosophical minefield. For example, you seem to assume that the process of 'observing' mental imagery is 'direct observation of our thoughts', but this is a very troublesome assertion to make.
First, what exactly does it mean to 'observe' a mental image? Mental images are definitely not like 'pictures in the head' which need to (or even can) be observed in the same way that we observe, say, the view from a window. The exact status of 'mental images', and what exactly is our relation to our own mental images, is a difficult and controversial issue, but it is clear that whatever they are, they are certainly not anything much like the things we actually see. (They seem to deserve the label 'image' largely because they involve some of the same neural machinery that is used when we really do observe; but we don't have eyes inside our heads.) Several psychologists have argued that there are in fact no such things as mental images, and certainly every workable model of them involves something much more like a propositional representation than anything like a picture.
But in any case, even if we accept that mental images exist, on what grounds do you conclude that we 'observe' them *directly*? If this means without any intervening mental representation, there is no evidence that we do in fact observe anything about ourselves in such a 'direct' way, or even what that could possibly mean; and if it does not mean that, what exactly does it mean?
>
> >"every cognition is determined logically by previous cognitions."
>
> By logically, he meant by deduction, induction, or abduction.
> The third is extremely important, because it allows any new
> hypothesis to be introduced or generated by chance. But before
> it can be accepted as "knowledge", it has to be tested against
> "facts" by induction and deduction.
Thanks also for this explanation. Abduction would include what I described
as the generation of thoughts by chance. I think I was thrown off the track
by the phrase "determined logically by previous cognitions" -- especially
the word "determined" -- since in the case of abduction a unique hypothesis
may not be determined by previous cognitions.
It may not follow deductively from them, but it may be determined by them, in the sense that some deterministic psychological mechanism may generate the abductive conclusion from the prior cognitive state. Given the time Peirce was writing, it was maybe expecting too much for him to make such a distinction, however.
Also, the value of a
hypothesis may need to be tested by later facts, not just prior facts.
> >"We have no conception of the absolutely incognizable."
>
> This seems to me to be obvious. We might hypothesize that
> some parallel universe exists that can never interact with
> us in any way. But then that is pure fantasy. It is indeed
> a conception, but calling it a conception of anything that
> exists is totally unwarranted.
But Peirce doesnt say that it exists, does he?
The only way I can make sense of this sentence is as a tautology, similar in logical structure to the assertion that you cannot point at something that cannot be pointed at. If there were an English word for being impossible to be pointed at ("inpointatizable", maybe) the sentences would even look alike. However, I can imagine a Thomistic objection along the lines that it is impossible to even *refer* to the absolutely incognizable, in which case the sentence would be meaningless. Which I have to say is the likeliest conclusion in any case.
<snip>
What I tried to do was to discuss the possibility that there may be limits
to what we can understand, i.e. things that are uncognizable.
This is kind of obvious, isn't it? For example, none of us can hold more than about a dozen things in our attention span simultaneously. I am sure that there are patterns in every raindrop which are many orders of magnitude more complex than I could understand in a lifetime. I know there are truths of arithmetic of the form n+m=k (where the letters stand for integers) which I can never understand since the entire human race will not survive long enough to write them down. There really is no need to cite Turing and Goedel in support of a platitude.
I mentioned
the results of Turing and Godel, along with the claims by some physicists
(e.g. Feynman) that there are some aspects of quantum physics that are
beyond our understanding.
Can you cite that claim of Feynmans?
Godel's result has been cited by Penrose to argue that there are limits to
artificial intelligence.
Penrose argues not that AI has limits (with which I think almost anyone might agree), but that human intelligence is not computational in nature and is forever beyond the reach of AI.
Some have replied that if such limits apply to
artificial intelligence, then they also apply to human intelligence.
There are better replies, the best of which is that his arguments are just plain wrong (and if they are taken seriously, then they are based on a paradox.) For details see:
Why Godel's theorem cannot refute computationalism" ( Laforte, Ford & Hayes)
AI Journal, 1998
Pat Hayes
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