Two Dogmas of Empiricism: Conclusion

By Hanno

Quine argues that "our statements about the external world face the the tribunal of sense experience not individually, but only as a corporate body."(p. 41.) Individual sentences are part of, or implied by, whole theories, and the theories themselves are malleable. Quine cites Duhem as holding the same view. No sentence can be empirically falsified simply because other sentences in the theory can be altered to keep the sentence as 'true.' Let us suppose that we have a theory about how the planets move around the sun, and let us suppose that we predict to see planet x at a particular point in the sky at some time t. We then run the experiment, and discover that the planet does not appear where we thought it would. Is the sentence "planet x at a particular point in the sky at some time t" false? If the positivists are right, the answer must be 'yes.' But maybe the problem is not with the claim about where the planet will appear, but about how light behaves. Then the planet really is there, but we are seeing it in a different place. Science is actually full of just these kinds of examples. Indeed, maybe the observation itself is poorly made. We can even throw out the apparent observation when it conflicts with deeply held theories. In fact, we do so all the time.

On quines view, our theories about the world are radically underdetermined by the data, so that multiple theories explain and predict the same data, whether the theory is about science or history. As he puts it:

"The totality of our so-called knowledge or beliefs, from the most casual matters of geography and history to the profoundest laws of atomic physics and pure mathematics and logic, is a man-made fabric which impinges on experience only along the edges.... the total field is so underdetermined by its boundary conditions, experience, that there is much latitude of choice as to what statements to re-evaluate in light of any single contrary experience. No particular experiences are linked with any particular statements..."

He continues:

"Even a statement...can be held to be true in the face of recalcitrant experience by pleading hallucination or by amending certain statements of the kind called logical laws."

Not only is any statement not falsified by any particular observation, no statement is immune from revision. Even the laws of logic are revisable. We can, for example, give up the law of excluded middle. Some think we should give up the law of non-contradiction. We play with the axioms of geometry, of set theory, and these changes effect the theorems that are then true or false. In short, just as there is no pure synthetic claim, there is no pure analytic claim , either, at least not in the way Kant and others imagines, claims that are true no matter what.

We posit metaphysical entities to account for what we see, like physical objects, and these are not reducible to experiences. The same is true of God and gods. Which metaphysics we adopt is a question for which theoretical framework accounts for our experiences better. But in principle, there is no difference between ontology and natural science.

If asked whether or not sets or numbers exist, Carnap writes that it depends on the linguistic framework we choose, that there is no matter of fact which determines which framework we ought to use. For Quine, the exact same is true of questions in natural science. And we choose our linguistic framework not on the basis of many different reasons, not merely experiential. Hence, conservatism, simplicity, explanatory power, etc., all help choose which theory, and hence which ontology we accept.

Two Dogmas of Empiricism, part II for real

by Hanno

The best way to read the first part of 2 dogmas is as an attack on the metaphysics of intensions. Logicians make a distinction between the extension of a predicate and the intension of a predicate. Consider a predicate like 'has a kidney.' There is a set of objects which satisfy that predicate, and that set is the extension of the predicate. Some other predicates have the same extension, as, in the classic example, 'has a heart.' The set of objects which have a kidney is identical to the set which has a heart, so the extentions of both predicates is the same. But what it means to have a kidney is different than what it means to have a heart. The meaning of the predicate is called its intension.

So all analytic claims are claims which share not just extension, but intension, i.e. they share meaning. Thus the predicate 'is an unmarried male' and 'is a bachelor' share not just extentions, but meaning, too, i.e. intensions, and because of that the claim 'All bachelors are unmarried males' is an analytic claim. We saw how the Logical Positivists used the distinction between analytic and synthetic claims in their philosophical analysis. But they never show just what these intensions actually are, nor how we can tell when one predicate has the same meaning as another predicate. And as empiricists, this knowledge must either be through logic, or empirical. But Quine in essence shows it can be neither.

Quine exempts from his analysis all truly logical tautologies. Those are statements that are true under all interpretations, from a logical point of view. He also does not object to any explicit definition. So his objection applies only to non-explicit, non-logical assertions of analyticity.

Now the logical structure of 'All bachelors are unmarried men' looks something like '(x)[Bx>(~Mx.Nx)]', where '(x)' is read as 'for all x', and 'Bx' is 'x is a bachelor,' '>' is the material conditional, '~' is the negation, 'Mx' is 'x is married' and 'Nx' is 'x is a man.' Read in its logicese, For any x, if x is a bachelor, then it is not the case that x is married and x is a man.' But this is not a tautology, for we can plug in (interpret) B, M and N in such ways that make it false. For example, if 'B' is 'x is a bat,' 'M' is 'x flies' and 'N' is 'x eats nerf balls,' then the sentence says 'for anything, if it is a bat, then it does not fly and it eats nerf balls,' which is surely false, unless there is something about bats that, really, someone should have told me.


But then it is obvious that all bachelors are unmarried is not known or explained through logic. If not by logic, how? Surely we cannot know the similarity of meaning empirically. If they were known empirically, then we would not know them with necessity or with certainty. A dictionary follows how we use language, and the definitions contained document the meaning of words, but the dictionary could be wrong, and are not necessarily true, or else meanings could never change.

How do we know what the meaning of 'has a heart' is? Answer: only by its extension. But then intension is just a sham, it can carry no philosophical weight. The meanings of predicates are not some entity to be discovered or uncovered. Any knowledge we have of that meaning comes by pointing to the things that have the property, i.e. by exntension. It follows that we can get these radically wrong, as we point to all the red balloons, and say 'balloon.' Then someone points to a red shirt, and we say 'balloon.' We only know what we mean because we have pointed to similar things, but the number of similarities and differences are endless, so we do not know if we latch onto the right similarity, the right difference. So, too, with 'bachelor' and 'unmarried man.' We know these terms by generalizing over the instances we have seen, but we can always be generalizing over the wrong properties.

Except... if we operationally define our terms. If we let how we know whether something or is not of a certain type define that type. Then if the method of verification (or falisfication) is the same, we can know that the meaning is the same. This does not use intensions, but is acceptable by the logical positivists. But can we reduce language, reduce the claims we make in language, to its method of verification? The positivists always assumed the answer was 'yes.' Carnap does is best to show it in his master work, The Logical Structure of the World. But they were wrong to assume it, and Carnaps' works shows vividly why it is impossible. And with that, verificationism, or falsificationism, go out the window.

That story next.