 From the Groundwork on, Kant’s objections to sentimentalism concentrate on what he takes to be its fatal flaw. No empirical principles can ground moral laws because such laws bind all rational beings universally, necessarily, and unconditionally. The authority of empirical principles, by contrast, depends on contingent aspects of human nature (G 4:442–43). Furthermore, variance in moral feelings makes them an inadequate standard of good and evil (G 4:442). Moral feelings cannot be the source of the supreme moral principle because the supreme moral principle holds for all rational beings, whereas feelings differ from person to person (M 29:625). If duty were grounded in feeling, morality would bind some people (e.g., the tender-hearted) more strongly than others. Even if people were in complete agreement regarding their moral feelings, the agreement would be a contingent matter, and thus an inadequate ground for the moral law, as Kant understands it. Indeed, if morality were grounded in feeling, it would be arbitrary: God could have constituted us so that we would get from vice the pleasurable, calm feelings of approval that we now (allegedly) get from virtue (M 29:625). So for Kant, the contingency of the ground of obligation offered by moral sense theories renders those theories inadequate; only a priori determining grounds will do.