David Lewis on Philosophical Method

“The reader in search of knock-down arguments in favor of my theories will go away disappointed. Whether or not it would be nice to knock disagreeing philosophers down by sheer force of argument, it cannot be done. Philosophical theories are never refuted conclusively. (Or hardly ever. Gödel and Gettier may have done it.) The theory survives its refutation—at a price. Argle has said what we accomplish in philosophical argument: we measure the price. Perhaps that is something we can settle more or less conclusively. But when all is said and done, and all the tricky arguments and distinctions and counterexamples have been discovered, presumably we will still face the question which prices are worth paying, which theories are on balance credible, which are the unacceptably counterintuitive consequences and which are the acceptably counterintuitive ones. On this question we may still differ. And if all is indeed said and done, there will be no hope of discovering still further arguments to settle our differences.

It might be otherwise if, as some philosophers seem to think, we had a sharp line between “linguistic intuition,” which must be taken as unchallengeable evidence, and philosophical theory, which must at all costs fit this evidence. If that were so, conclusive refutations would be dismayingly abundant. But, whatever may be said for foundationalism in other subjects, this foundationalist theory of philosophical knowledge seems ill-founded in the extreme. Our “intuitions” are simply opinions; our philosophical theories are the same. Some are commonsensical, some are sophisticated; some are particular, some general; some are more firmly held, some less. But they are all opinions, and a reasonable goal for a philosopher is to bring them into equilibrium. Our common task is to find out what equilibria there are that can withstand examination, but it remains for each of us to come to rest at one or another of them. If we lose our moorings in everyday common sense, our fault is not that we ignore part of our evidence. Rather, the trouble is that we settle for a very inadequate equilibrium. If our official theories disagree with what we cannot help thinking outside the philosophy room, then no real equilibrium has been reached. Unless we are doubleplusgood doublethinkers, it will not last. And it should not last, for it is safe to say that in such a case we will believe a great deal that is false.

Once the menu of well-worked-out theories is before us, philosophy is a matter of opinion. Is that to say that there is no truth to be had? Or that the truth is of our own making, and different ones of us can make it differently? Not at all! If you say flatly that there is no god, and I say that there are countless gods but none of them are our worldmates, then it may be that neither of us is making any mistake of method. We may each be bringing our opinions to equilibrium in the most careful possible way, taking account of all the arguments, distinctions, and counterexamples. But one of us, at least, is making a mistake of fact. Which one is wrong depends on what there is.”

~ David Lewis, Philosophical Papers Vol. 1