The Cold War integration of rational choice theory into philosophy brought a problem: Cold War philosophy holds that anything rational must be reached via a choice among alternatives, but philosophy has traditionally had little truck with theory-choice. From its very beginnings, philosophers have sought to eliminate all alternatives to their views, to come up with arguments which had to be accepted. This reached an apogee in Spinoza’s Ethics, from start to finish a single deduction more geometrico from first principles; but traces of it can be found wherever a philosopher seeks a knock-down argument. How to replace this ancient “necessitarian” approach with modern market choice?
David Lewis solved the problem in the Introduction to volume I of his Philosophical Papers (Oxford: 1983), by denying (in a Quinean spirit) what Hans Reichenbach called the “autonomy of problems,” or rather the autonomy of opinions. The aim of philosophy, for Lewis, is to bring one’s opinions into “equilibrium”—apparently a sort of Pareto-efficient state in which changing any of one’s opinions leaves one worse off. “Being worse off” is parsed as having opinions that contradict each other or that depart too greatly from compelling common sense—from what “we cannot help believing outside the philosophy room” (x).
Inside that room, philosophers determine which other opinions, philosophical or commonsensical, must be abandoned if we are to accept a given opinion. Philosophy “sets the price” for an opinion or a conjunction of opinions, an “equilibrium” (ix). This price-setting, as Lewis develops it (he develops it only slightly in this very short text). has two sides. Logic traces out the interrelations of opinions with respect to their consistency or inconsistency; “when all [this] is said and done,” the philosopher measures the distance between the resulting theory and common sense. The result is the price. Theories, or opinions, or equilibria, are thus opted for under preferences for consistency and consonance with common sense, which itself is another form of consistency among opinions.
With this, Lewis accommodated philosophy to Cold War rationality—but at a price. On the surface, the price seems to be the abandonment of the quest for knock-down arguments, a ban which Lewis openly announces. But abandoning philosophy’s ancient quest for knock-own arguments piggybacks on a deeper change, and Lewis’ innovations are far more radical than they appear.
Lewis’ account of quasi-Pareto-efficient equilibria of opinions sounds remarkably like a coherence theory of truth, right down to his thoroughly Hegelian remark that “philosophical theories are [almost] never refuted conclusively” (ix). But Lewis does not conflate such efficiency with truth; philosophy’s goal is not truth but logically consistent and empirically consonant equilibria among opinions. Lewis’ views on truth, here, implicitly trade on the idea that truth is a relation holding between opinions and matters of fact. Though truth can be had, logical method will not give it to us: facts of matters make theories true or false irrespective of how much consistency and consonance those theories have achieved (xi). Hence Lewis’ lament, in the third paragraph of the Introduction, that he is not nearly unsystematic enough. Coherence and consistency are great things, but apparently they are not truth.
The real price, then, is this: philosophy as the tracing-out of logical relations among opinions, and the gauging of their consonance with common sense, is no longer a search for truth. It is a search for a set of prices. The abandonment of knockdown arguments follows from a deeper abandonment: that of truth as philosophy’s goal.
Lewis’ Introduction is thus an epochal moment in the history of analytical philosophy and, I suggest, of philosophy in general (more on that in a subsequent post). It is foreshadowed in Quine’s metaphor of the web of beliefs (which touches reality only at its edges), and in Davidson‘s metaphor of meaning as truth-conditions (for that, too, is a metaphor: as I pointed out in my The Company of Words, Northwestern 1994, pp. 335-336, the locutions with which Davidson regularly discusses that doctrine are precisely those that, he says, properly characterize metaphor).
The idea that opinions can be brought into Pareto efficiency is also a metaphor, a carrying-over from economics. Opinions are *like* commodities; they can have positive or negative utility—depending on the logical price we pay for them.
If we take Davidson’s “A Nice Derangement of Epitaphs” (1986) to be the most radical statement of his metaphor, then we should say that between 1983 (the date of Lewis’ Introduction) and 1986 the nature of their discipline changed, and in a very fundamental way: philosophy ceased to be a search for truth and became the confection of metaphors.