I was thinking of writing up some kind of reply to “Scott Soames’s reply”:http://www-rcf.usc.edu/~soames/replies/Rep_Weatherson.doc to my reply to his book. But the threat of an infinite regress was looming, and I thought it would be more fun to ruminate on his title: “What we Know Now That We Didn’t Know Then”. Because there are some fun puzzles about philosophical knowledge that the end of Soames’s book brings up.

Let’s start first with a puzzle about discovery. Consider the following situation.

* _p_ is a true philosophical claim.
* S1 is the first to believe that _p_, but on the basis of a bad argument, so she doesn’t know that _p_.
* S2, knowing that S1 believed that _p_, comes up with the first good argument that _p_, and so is the first one to know that _p_.

Question: Who, if anyone, discovered that _p_?

To make things more concrete, let _p_ be the proposition that there are necessary a posteriori truths. Kripke wasn’t the first philosopher to _believe_ that _p_ is true. He wasn’t even the most prominent, I think. If I’m reading him aright, Aquinas holds that God’s existence is “necessary”:http://www.newadvent.org/summa/100203.htm “a posteriori”:http://www.newadvent.org/summa/100202.htm. I imagine Aquinas wasn’t the first to believe this about God, or more generally about propositions to do with the divine, but for the sake of the example let’s say that he was so he can fit S1 in the schema. I don’t know if Aquinas bothered to do the simple inference to the claim that _some_ true proposition is necessary a posteriori, but I think we can credit him with tacitly believing this, as I’ll do for the sake of the example[1].

Now many of us, probably most of us who aren’t Thomists, think that Aquinas’s reasoning did not grant him _knowledge_ that there are necessary a posteriori truths. But does his true belief suffice to block Kripke’s claim to have _discovered_ that there are necessary a posteriori truths? Whatever intuitions I have say _yes_. (At least assuming Kripke knew of Aquinas’s views. But I suspect he did as a tolerably well read philosopher. And assuming of course that my reading of Aquinas on this point is right, which is always dubious.)

Of course, Kripke discovered plenty of necessary a posteriori truths. But that’s different from discovering that there are any. (One can discover lots of spiders without discovering that spiders exist.) And he discovered the first good argument that there are necessary a posteriori truths (I assume, though Thomists might beg to differ). But I don’t think it’s right to make the propositional discovery claim.

It doesn’t seem like I can discover philosophical truths by going back through old philosophical works, finding plausible claims that are badly argued for, and finding arguments for them. That might be a good way to discover interesting philosophical _arguments_, but I don’t think by doing this I’d get credit as the discoverer that various philosophical claims are true. Not that I’d mind – I’m more interested in discovering arguments than anything else.

This does raise an awkward question: who (in our example) did discover that there are necessary a posteriori truths? I think the answer is _no one_. Aquinas didn’t discover this. Discovering that something is true requires having a good argument that it is true, and Aquinas didn’t have such an argument. Discovering that _p_ might even require knowing that _p_. But we don’t need such a strong claim to deny that Aquinas discovered that there are necessary a posteriori truths. And I argued above that Kripke didn’t discover this either.

My position here has the unfortunate consequence that a truth came to be known without anyone discovering it. I think that’s a consequence that we can live with, indeed that we have to live with in some circumstances. Consider the following kind of case, which I imagine happens all the time in mathematics. A hypothesis _q_ is widely believed, perhaps because there is a purported proof of it, and is used in the proof of many theorems. It turns out, however, that _q_ is false, and something close, _q_* is true. (Imagine that _q_* is a version of _q_ with slightly restricted quantifiers.) The difference between _q_ and _q_* is not relevant for the proofs in which _q_ was used, and in many cases it’s too trivial to even publish a note showing this. Now consider the theorem at the end of one such proof. We know now that it’s true. But who discovered it? The person who proved it on the basis of _q_? Arguably they didn’t know it was true, because _q_ is false, and hence didn’t discover it. The person who proved _q_*? That will lead them to getting an enormous amount more credit than we feel they intuitively deserve. I think nothing to be said here other than that we came to know the theorem without anyone actually discovering it.

Well, this is all assuming that Kripke did know that there are necessary a posteriori truths. And we might question that. Rather than get the details right, I’ll work through an imaginary example to illustrate why I’m worried here. Expand the story above in the following way.

* S2 provided a good argument for _p_, but also a bad argument that _p_, and she insisted that each argument is sound.

Does the bad argument defeat S2’s claim to knowledge? It’s somewhat plausible that it does. It certainly suggests that S2’s judgment around here is fallible, perhaps so fallible that judgment is not a ground for knowledge. If we put things in reliabilist terms, S2 is 1 for 2 in detecting good arguments for _p_. And whatever the threshold for reliability is, I imagine it’s normally meant to be above 50%. Well perhaps that’s the wrong reference class. But I hope you see why there’s a plausible threat to knowledge here.

Now that is arguably just what happened with Kripke. Here, for instance, is the abstract of a paper by Soames on Kripke’s work.

bq. Kripke’s discovery of the necessary aposteriori is placed in historical and philosophical perspective. I argue that his first, essentialist, route to the necessary aposteriori has led to a distinction between metaphysical and epistemic possibility that is an important advance, while his second route to the necessary aposteriori has led to an attempted revival of pre-Kripkean orthodoxy which both threatens that advance, and leads to suspect philosophical results – including his own flawed argument against mind-body identity theories.

Sounds to me like Kripke fits the description of S2, and there’s reason to deny that in general S2 knows the philosophical claim in question.

Note that if we think discovery that _p_ requires knowledge that _p_, as I think is at least plausible, we have a pretty clear case here of knowledge without discovery. The first critic who reads S2’s work and realises that the first argument is good but the second is lousy is the first person to know that _p_. But surely _they_ don’t discover that _p_. So we can accrue philosophical knowledge without anyone making a philosophical discovery. So the initially attractive analysis of _S discovered that p_ as _S is the first to know that p_ is sadly mistaken.

fn1. I’m relying here on a fairly literal reading of the Third Way, and I’m sure there are reasons not to read it this way. One such reason might be that if read literally, it contains many modal fallacies. But as far as I can tell, _any_ way of reading it will contain many modal fallacies, so charity doesn’t point against the literal reading here. Still, I’m no Aquinas scholar so perhaps there are better reasons to otherread him here. Admittedly the Third Way doesn’t look particularly a posteriori either, but I’m sure Aquinas _intended_ it to be an a posteriori argument.