Arguments against physicians’ claims of a right to refuse to provide tests or treatments to patients based on conscientious objection often depend on two premises that are rarely made explicit. The first is that the protection of religious liberty (broadly construed) should be limited to freedom of worship, assembly, and belief. The second is that because professions are licensed by the state, any citizen who practices a licensed profession is required to provide all the goods and services determined by the profession to fall within the scope of practice of that professional specialty and permitted by the state, regardless of any personal religious, philosophical, or moral objection. In this article, I argue that these premises ought to be rejected, and therefore the arguments that depend on them ought also to be rejected. The first premise is incompatible with Locke’s conception of tolerance, which recognizes that fundamental, self-identifying beliefs affect public as well as private acts and deserve a broad measure of tolerance. The second premise unduly (and unrealistically) narrows the discretionary space of professional practice to an extent that undermines the contributions professions ought to be permitted to make to the common good. Tolerance for conscientious objection in the public sphere of professional practice should not be unlimited, however, and the article proposes several commonsense, Lockean limits to tolerance for physician claims of conscientious objection.