[hist-analytic] A posteriori knowledge of necessary truths
Baynesr at comcast.net
Baynesr at comcast.net
Sat Dec 18 13:23:58 EST 2010
Nice to hear from you again, Roger.
The context I had in mind was the usual discussion of a posteriori knowledge of necessary truths. Aside from that, I don't think I can say much, if anything, about context. I don't think logical constructions really supply a useful methodology. It's been tried in philosophy of language with results accruing only to insights not requiring the logical rigamorole. in the first place. In other words, system building of this sort is typically an "unnecessary" shuffle. This is not to say that I don't believe first order logic (with identity) is not useful, or even that a model theoretic semantics of modal notions doesn't supply some illumination into a certain limited area of interests, only that it is "brittle" and often capricious. So we differ methodologically. Now to your second point.
The first part I accept, since I don't see that it contradicts what I've said etc. and I think it is pretty much right: knowledge of meanings is a posteriori etc. That's fine with me. But now the concluding part.
Introducing an existential won't entail that the sentence in which it occurs is de re. For example '(John believe (Ex)Fx)' has a de dicto reading; a de re reading would allow for wide scope: '(Ex)(John believes Fx)'. Here the quantifier "reaches" from outside the belief context <g> into the belief context. Here we have a de re reading. Compare: 'There is someone John believes is a spy' and 'John believes there is someone who is a spy'. Quite different; both existentials, but the semantics differs (on the usual assumptions). I conclude with a point on rigid designation.
You are right to say that the reference of a rigid designator is fixed by its meaning; but that it is a rigid designator is not fixed by its meaning. So even though we come by meaning by way of experience, we do not come by our understanding that a term is rigid by way of experience; that is a semantical feature of names, such as 'gold', one that has no correlative in experience. I cannot *know* a term designates the same thing in all worlds if all I know is that it designates in this one; I have to know something about the semantics of the term that many competent speakers know nothing about.
I think I've covered all the bases. Not sure.
----- Original Message -----
From: "Roger Bishop Jones" <rbj at rbjones.com>
To: "hist-analytic" <hist-analytic at simplelists.co.uk>
Sent: Saturday, December 18, 2010 10:48:13 AM
Subject: Re: A posteriori knowledge of necessary truths
Here are some observations on your recent message on the
FIrst, I doubt the soundness of your method.
In order to reason soundly you must do so in a context which
is sufficiently well understood for its principles and rules
to be definite and their consistency strength establishable.
I know no way of doing this other than though the
construction of one or more formal models in a well
established logical system.
By this means you would ensure the soundness of your
reasoning, and can then debate how well your models
correspond to ordinary or philosophical usage of natural
languages on the relevant topics.
Second (if I might now disregard my own advice are reason in
an informal context), when making judgements about whether
some knowledge is a priori or a posteriori it is essential
to differentiate between information obtained by experience
according to whether it contributes to establishing the
meaning or the fact.
Our knowledge of the meaning of a natural language is of
course a posteriori, and if the language contains rigid
designators then (in any model I would be likely to work
with) the designatum of a rigid designator will be fixed by
its meaning (if it is not so fixed then it cannot be rigid).
In that case the use of experience in discovering the
designata in an equation of rigid designators will be a case
of knowing the language rather than of knowing the fact.
The fact will be an instance of the reflexivity of identity
and will be knowable a priori.
I would also myself not accept your opinion that the
introduction of an existential quantifier makes a de re
proposition from one which is not de re.
This sounds like the supposition that all existence is
contingent, which for anyone sympathetic to Carnap's stance
on abstract ontology will not be the case.
Sorry not to have undertaken a more thorough critique, but
my dominant sentiment is my first, that formality is
essential in dealing with logical problems of even this
level of complexity.
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