A sound intuition animates Professor Denning's defense of the doctrinal status quo under the dormant commerce clause: the courts should not lightly abandon well-established constitutional canons. I nevertheless remain unconvinced by Professor Denning's effort to justify the long-standing interpretation of the dormant commerce clause as forbidding taxes which discriminate against interstate commerce. Whatever the historical justification for this constitutional precept, its past utility, or its visceral appeal, dormant commerce clause nondiscrimination is today doctrinally incoherent in tax contexts. The problem is not one of borderlines and close cases. Rather, at its core, the notion of dormant commerce clause tax nondiscrimination currently rests on two untenable distinctions: the distinction between tax incentives and direct expenditures and the distinction between tax provisions which are deemed discriminatory and those which are not. For two reasons, neither of these distinctions is today workable or persuasive.