Londoner wrote:This just chases its tail. If a proposition was knowable non-empirically then it wouldn't be empirical knowledge. As to whether we could gain empirical knowledge in some other way, that is the point at issue. Personally I think the answer looks like 'no' because nobody has come up with a convincing example.
Knowledge which hasn't been acquired by empirical means isn't empirical knowledge.
As for the question of convincing examples, there are doubtless numerous convincing examples of analytic knowledge a priori at least, which is logical/conceptual/logico-conceptual knowledge (given the definition of an analytic truth as an explicit or implicit logical truth). The radical-empiricist assertion that not even analytic truths such as "Bachelors are unmarried" are knowable a priori seems indefensible to me.
What about convincing examples of synthetic knowledge a priori? Well, it turned out that such examples are very hard to come by. But what about e.g.
"Dogs aren't numbers" or
"Holes don't have holes"? If these were analytic truths, they would be synonymous with a tautology. And in order to show they are, you have to validly transform them into a tautology (logical truth). As far as I'm concerned, I'm not able to do so, which is a reason for me to regard them as synthetic truths—and as synthetic truths which are knowable a priori. For I don't think I have to observe dogs or holes in order to be able to come to know that dogs aren't numbers and holes don't have holes.
The hard problem of drawing a clear and precise distinction between analytic propositions/truths and synthetic propositions/truths is primarily a problem for moderate empiricists, since radical empiricists don't have to care about it, given their absolute denial of the possibility of a priori knowledge, be it analytic or synthetic.
Londoner wrote:Teuton wrote:...However, this is not what "There is no synthetic a priori knowledge" means. It means that all synthetic knowledge is based on or derived from experience.
I did not say that was what '(no) synthetic a priori' meant. As for your own gloss, what does it mean? Why does it use the word 'synthetic'? In what way is your meaning different from: 'empirical knowledge is derived from experience'?
"Synthetic knowledge" is not synonymous with "empirical/a posteriori" knowledge. The analytic/synthetic distinction is a
logical/logico-semantic one, whereas the a priori/a posteriori distinction is an
epistemological one:
*
Analytic knowledge is knowledge of propositions whose truth depends on and is determined by nothing beyond their form and meaning; and
synthetic knowledge is knowledge of propositions whose truth depends on and is determined by something beyond their form and meaning.
*
A priori knowledge is propositional knowledge whose source is different from perception, introspection, and recollection, i.e. whose source is rational intuition; and
a posteriori knowledge is propositional knowledge whose source is different from rational intuition, i.e. whose source is perception, introspection, or recollection.
Londoner wrote:But remember, there is no point in you telling me what you consider it means. We were discussing a quote which claims the phrase is self-contradictory. If somebody - me for example or any other philosopher - does not understand it in the way claimed, then the criticism doesn't apply.
What different ways of understanding are there in the context of empiricism?
Londoner wrote:Teuton wrote:The correspondence theory of truth is neutral between empiricism and rationalism, so we don't have to distinguish between "empiricist truth" and "rationalist truth".
Again, that isn't for you to say. The quote is saying what a third party, those 'empiricists' claim. Its truth depends on whether it is an accurate description of how those empiricists' might have used the word in that context (if they ever did)...(And assuming that you can bracket together Hume and Berkeley and Wittgenstein and Russell (?) etc. as if they all thought alike).
That's a red herring! For the empiricists and the rationalists do understand their own and their opponents' position sufficiently well.
Londoner wrote:If I wrote 'Atheists claim to know that it is true that God doesn't exist' we could construct a similar paradox; that this implies they have the God-like knowledge required to prove a negative, therefore the atheists must be claiming they are God. The atheists would reply; We don't claim to know absolutely God doesn't exist; what we say is that we have never seen God and nor can we see an argument for thinking he exists. Rather like the 'synthetic a priori'.
Knowledge claims entail (subjective) certainty. You don't claim to know that p unless you are certain that p. But mere belief doesn't entail certainty or a knowledge claim. Empiricists believe that all synthetic knowledge is based on experience, but their claim isn't itself knowable empirically. However, that empiricists cannot (and therefore shouldn't claim to) know that empiricism is true doesn't mean that they cannot justifiably, reasonably or plausibly believe it is, with that belief falling short of knowledge. Of course, if you uphold the general normative principle that one is never justified in believing what is unknown or unknowable, then one must stay agnostically neutral between empiricism and rationalism.
There is a difference between claiming that the truth of a synthetic proposition is not strictly knowable a priori, and claiming that there can be no belief-justifying a priori evidence for the truth of synthetic propositions. That is, there is a difference between saying that synthetic propositions cannot be known to be true in a non-empirical way and saying that they cannot even be justifiably believed to be true in a non-empirical way, in the sense that there cannot be any non-empirical evidence for their truth, be it conclusive or inconclusive.