Abstract: The Supreme Court is conspicuously uneasy about its Chevron framework, which requires courts to defer to agency interpretations of law, so long as those interpretations are “reasonable.” One of the principal manifestations of its uneasiness is the “major question” doctrine, which makes Chevron inapplicable to questions of great “economic and political significance.” But the major question doctrine is actually two separate doctrines. The weak version is a kind of “Chevron carve-out,” meant to ensure that courts exercise independent judgment, and so do not defer to agencies, with respect to the meaning of statutes as applied to especially important questions. By contrast, the strong version flatly prohibits agencies from interpreting ambiguous statutes so as to assert broad authority over the private sector. Both versions of the major question doctrine can claim a connection to the nondelegation doctrine. The arguments on behalf of the weak version are very different from the arguments on behalf of the strong version.