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"Kripke, Quine, the “Adoption Problem” and the Empirical Revision of Logic"

The idea that there is an ‘adoption’ problem for certain basic principles of logic was originally proposed and developed by Saul Kripke in seminars in Princeton in the mid-1970s, although Kripke himself published nothing on the topic. Kripke’s discussion was aimed at making trouble for two major positions in the philosophy of logic, positions that were the focus of much discussion at the time. The first was Quine’s view that logic is just part, albeit a ‘web-central’ part, of empirical theory, that having a logic is accepting a set of beliefs about logical truth, and that logics are freely adoptable and empirically revisable. The second was Putnam’s Quine-inspired proposal that quantum physics gives us reason to reject the classical distributive principles for conjunction and disjunction and so, for broadly empirical reasons, to ‘adopt’ a logic that does not incorporate them.

Kripke’s contention was that Quine’s and Putnam’s views depended on a confused conception of the relation between logical practice, on the one hand, and the acceptance of statements of logical laws, on the other. His idea seems to have been that, if the relation between these two notions were understood aright, the temptation to think that logical inferential practice might be modified under pressure from empirical discoveries would disappear.

In this talk I’ll first offer a rough statement of the problem—I’ll call it the Original Adoption Problem (OAP) —that seems to be doing the rounds at the moment, then argue that it depends on a questionable assumption, before using that discussion as a springboard for developing a different version of an adoption problem. I’ll argue that, for a significant class of basic logical principles, there is indeed a difficulty in seeing how they might be ‘freely adopted,’ thereby vindicating a substantial part of Kripke’s original claim.

If certain basic logical principles may not be ‘freely adopted’, that is not a problematic contention per se. Rather it is a problem for certain views about the status of logic, including pre-eminently the quite widespread contemporary “anti-exceptionalism”, spawned by Quine’s “Two Dogmas”. Anti-exceptionalism holds that we enjoy the same kind of epistemic freedom in proposing logical principles and subjecting them to empirical test as we have with scientific conjecture in general—indeed, that the epistemology of logic is in no interesting way different from that of theoretical science. There are actually two different contentions in play here: that logical principles, like scientific hypotheses, may be freely accepted and, again like scientific hypotheses, that they are open to rational rejection on purely empirical grounds. Both are integral to the Two Dogmas picture of what it is to manage in a rational fashion a comprehensive system of belief, but they are separable claims. In the concluding part of the talk, we will turn to the question, specifically, of the empirical revisability of logic, arguing that when proper attention is paid to the distinction between inferential practice and logical theory, it does indeed emerge that anti-exceptionalism, in full generality, is untenable.

*Note: Joint collaboration with Professor Boghossian.