[This originally appeared on Language Log in February 2010, as a guest post.]
The United States Tax Court recently decided that payments for sex-reassignment surgery are deductible as medical expenses. Among the 15 judges, there were six separate opinions, with five of the judges dissenting. Most of the debate dealt with questions like whether Gender Identity Disorder is a “disease” (a key term in the statue) and if so whether sex-reassignment surgery, which doesn’t change the patient’s subjective sense of gender identity, constitutes a “treatment” for the disease (ditto).
Those are issues with interesting linguistic dimensions, but what I want to talk about here is a different aspect of the case: the dispute about how to interpret disjunction under negation—i.e., how to interpret expressions such as I don’t know anything about linguistics or tax law (with don’t signaling negation and or signaling disjunction).