Carnap and Quine Compared

Carnap

Carnap thinks there is nothing more to making an ontological commitment than adopting a framework, which is a purely pragmatic matter. Ontology is no big deal, in fact,

it will be shown that using [a language referring to abstract entities] does not imply embracing a Platonic ontology, but is perfectly compatible with empiricism and strictly scientific thinking. ... It is hoped that clarification of the issue ... may help [those who would like to accept abstract entities ...] to overcome nominalistic scruples. (Carnap, 13)

The internal statement, for example, "numbers exist," which one accepts in accepting a certain framework, is no big deal because it is just a matter of following certain linguistic rules. The external statement, on the other hand, is "noncognitive," it, roughly speaking, makes no sense. There are no facts which our views on such matters need to respect. The external statement is not true or false in the ordinary sense of fitting the facts. So, is Carnap a nominalist about numbers or a realist? No. He is neither. He is strongly antimetaphysical, specifically antiontological.

To put the view in a slogan: Ontology comes down to nothing more than the choice of a pragmatically useful language for whatever ones purposes happen to be.

Quine

This, I think, is characteristic of ... ontology: one who regards a statement on this subject as true at all must regard it as trivially true. ... Judged within some particular ontological scheme—and how else is judgment possible?—an ontological goes without saying, ... .

...

Judged in another conceptual scheme, an ontological statement ... may, with equal immediacy and triviality, be adjudged false. (Quine, p. 8)

Quine's "conceptual schemes" sound a whole lot like Carnap's frameworks. For both Quine and Carnap, ontological questions are answered by background assumptions, not (in the first instance) by external facts. However, Quine does not endorse a distinction between internal and external "versions" of metaphysical questions. For him, for someone with one conceptual scheme, it is true that numbers (actually, attributes) exist; for someone with another, false. Can one switch between conceptual schemes in the way Carnap thinks we can switch between frameworks? Quine is a realist. For him, what there is is part and parcel of ones conceptual scheme, and not something which one can put on or take off at will.

Quine has a big problem: he seems to be saying, simultaneously,

I have argued that the sort of ontology we adopt can be consequential—notably in connection with mathematics ... . Now how are we to adjudicate between rival ontologies?

...

In debating over what there is, there are still reasons for operating on a semantical plane. ...

...

Another reason for withdrawing ... is to find common ground ... . The collapse of the controversy into question-begging may be delayed.

...

Our acceptance of an ontology is, I think, similar in principle to our acceptance of a scientific theory, ...: we adopt, at least insofar as we are reasonable, the simplest conceptual scheme into which ... experience can be fitted and arranged. Our ontology is determined once we have fixed upon the over-all conceptual scheme which is to accomodate science in the broadest sense; and the considerations which determine a reasonable construction of any part of that conceptual scheme, for example, the biological or physical part, are not different in kind from the considerations whic determine a reasonable construction of the whole. (Quine, pp. 10–11)

Technical terms: myths and posits.

-- ShaughanLavine - 25 Jan 2008