The Tyranny of the Subjunctive

David J. Chalmers

Department of Philosophy
University of Arizona
Tucson, AZ 85721

[[Unpublished. Presented at Princeton in October 1998, at ANU in January 1999, and at the Idaho conference on "Truth and Meaning" in March 2000.]]


The above all seem to be intuitively correct, even though (1a) and (2a) have "metaphysically impossible" consequents.

What's the relevant difference? Indicatives take the antecedent as a hypothesis about the actual world, whereas subjunctives take it as a description of a way the world might have been but actually isn't (Fowler: "it belongs to utopia"). That is, indicatives consider the antecedent as actual; subjunctives consider it as counterfactual.

In terms of the 2-D semantic framework: evaluation of indicatives tracks the primary intensions of the expressions involved, whereas evaluation of subjunctives tracks their secondary intensions. "Metaphysical necessity" reflects secondary intensions, not primary intensions.


QUESTION: How to evaluate "S is true in W"?

SUBJUNCTIVE READING: "S is true in W" iff

INDICATIVE READING: "S is true in W" iff

The first tracks familiar "subjunctive" (utopian) evaluation of possibilities. The second tracks "indicative" (epistemic) evaluation of possibilities. (Is the epistemic possibility that W is actual an instance of the epistemic possibility that P?)

There are two resulting sorts of "necessity": subjunctive necessity and indicative (epistemic) necessity. And two sorts of "possibility", etc.

Plausibly: S is subjunctively necessary if S's secondary intension is true in all possible worlds. S is indicatively necessary if S's primary intension is true in all (centered) possible worlds.

e.g. S = "water is H2O". W = the Twin Earth world (with XYZ).

This mirrors the fact that the secondary intension of S is true in W, but the primary intension of S is false in W. So "water is H2O" is not indicatively (epistemically) necessary, although it may be subjunctive necessary.


In contemporary philosophy (post-Kripke), "necessity" (simpliciter) is always read as subjunctive necessity, and "P is true in W" is always evaluated by the subjunctive reading.

In fact: subjunctive conditionals *ground* the contemporary evaluation of statements in worlds, and the consequent analysis of necessity. Kripke's arguments in Naming and Necessity are always ultimately grounded in intuitions about subjunctives.

QUESTIONS: Why is this? Arbitrary? Argued or stipulated? Is indicative necessity an equally good candidate for "necessity"?

SYMMETRY THESIS: Indicative necessity is as good a candidate for "necessity" as subjunctive necessity. And epistemic evaluation is just as reasonable a reading of "P is true in W" as subjunctive evaluation.

If the symmetry thesis holds, it should be just as reasonable to say that:



(a) Indicative necessity is "merely epistemic".

(b) S is necessary <-> S "could not have been otherwise" -- subjunctive!

(c) Indicative necessity requires centered worlds.

(d) Subjunctive necessity supports quantified modal logic, whereas indicative necessity doesn't.

(e) The relevant indicative conditionals aren't true/false, just assertible, due to epistemic relativity. (e.g. Sly Pete)

(f) Some indicative "necessities" will vary in truth-value between users, as primary intensions of some terms (e.g. names) can vary between users.


Necessity plays a central role in almost every area of philosophy. So the analysis of necessity affects almost every area of philosophy. Kripke's analysis has been central in supporting essentialism in metaphysics, direct reference views in the philosophy of language, externalism in the philosophy of mind, and so on. Has led to a lot of interesting remaking of philosophical views, with "marvelous internal coherence". But.

Imagine an alternative universe in which Kripke* used indicative conditionals instead. His book Naming and Contingency might have

Imagine that the ensuing philosophical analysis of necessity had been as biased toward indicative necessity as recent philosophy has been toward subjunctive necessity. The resulting dominant views in various areas of philosophy might have been very different:

Neither our world nor W* is the right outcome. The best outcome, given the symmetry thesis, is one in which the notion of "necessity" is recognized as ambiguous. Kripke** (importantly) recognizes the modality of subjunctive necessity and its distinctive properties. This leads the pretheoretical notion of "necessity" to split into two varieties, along with two corresponding means of evaluation in possible worlds. As to specific philosophical areas: the outcomes here will depend on analyzing whether the modality in those areas is relevant qua subjunctive or qua epistemic.