THE PRACTICAL NECESSITIES OF PHILOSOPHICAL LIFE
Before I present my arguments against the legitimization argument, the autonomy thesis, and the bracketing strategy, however, I should make it clear what I am objecting to, and what I am not.
A bit of terminology: for the sake of concision, I will use the term “core accounts” for accounts of scientific representation, modeling, theory structure, idealization, explanation, confirmation, and the like—all aspects of scientific practice which are among the central epistemological and methodological focal points of the philosophy of science. This choice of label is not meant to imply that constructing accounts of such things is the core of the philosophy of science; it is intended only to reflect the fact that the project of constructing accounts of such things is at the center of some large part of the discipline, and closer to its core (these days, at least) than the attempt to construct accounts of the semantics and ontology of our ordinary and scientific discourse—the other sort of account to which I will need to make frequent reference.
First, then, I am not saying that all work on modeling, say, should grind to a halt until certain metaphysical questions about the existence and nature of models, mathematical structures, and fictional objects have been answered. It is a common enough situation in philosophy, as in other fields of inquiry, that the answer to one question depends in part on the answer to a number of other, equally difficult and uncertain questions. And it is a perfectly sensible way of coping with such situations, as a temporary measure, simply to assume something about the answers to those others questions. (Exactly what one assumes will not usually be an arbitrary matter, of course; typically it is a sort of educated bet.) Accordingly, I have no quarrel here with the philosopher of science who says, for example, “Here’s my account of scientific representation/modeling/theory structure/explanation/ ... ; note that it presupposes a certain sort of nominalism about mathematics,” or “note that it presupposes that there are fictional objects, and that they are abstract artifacts.” Of course, this does mean that in order to fully evaluate the account on offer, we will have to take a stand on whether the presupposed account of mathematical or fictive and metafictive discourse is correct; but again, that is a common enough situation in philosophy, and I have no axe to grind in this respect.
Someone who employs what I am calling the bracketing strategy is doing something quite different, however. Rather than making certain metaphysical commitments without necessarily regarding it as decisively established that they are the right commitments to make, she presents a core account which engages quite heavily in talk of models, mathematical structures, or fictional objects, and yet she simultaneously denies that she has thereby taken on substantive commitments with respect to the ontology of modeling discourse, mathematical discourse, or fictive and meta- fictive discourse. She thus insists that we can provide core accounts which provide satisfying answers to the questions we have as philosophers of science, and which do so in part by making free use of talk of models, mathematical structures, or fictional objects, without having to address the metaphysical issues in question. This is the claim that is my target here. And my aim in this paper is to critique a justification that has been offered for this autonomy thesis and the corresponding bracketing strategy, and, moreover, to make a case that the thesis is false and the strategy illegitimate.
A second, smaller point of clarification: neither am I insisting that philosophers of science who present the sorts of accounts in question should become metaphysicians (or philosophers of mathematics, philosophers of language, or aestheticians), even part-time. One reasonable way of proceeding is to turn to other philosophers who have thought long and hard about the nature and existence of mathematical structures, fictional objects, and the like for guidance on the answers to the metaphysical questions. That is one way of dealing with the fact that, if we as philosophers of science offer core accounts which rely heavily on talk of models, mathematical structures, or fictional objects, we have become hostage to the outcome of certain investigations in metaphysics. The most I claim is that we must admit that fact, and be responsive to it in some way or other.
These points of clarification out of the way, let me now turn to the central business of critiquing the legitimization argument and, furthermore, making it plain why I think the autonomy thesis false, and the bracketing strategy unjustifiable.
-  I have in mind, with the latter example, Amie Thomasson’s account of the ontology of fiction; see her Fictionand Metaphysics (1999) and my (forthcoming).