I argue that first-order moral theory often overlooks a crucial mistake: moral hubris. A moral view is guilty of moral hubris when it “goes too far”—that is, when it implies moral claims that fail to respect what I call the function constraint. This constraint sets the boundaries of what moral norms can demand while still qualifying as moral norms. It arises from the fundamental purpose or function of morality, where “morality” refers to our actual socio-cultural moral practice.

In short, moral hubris occurs when a moral theory advocates norms that conflict with the very purpose of moral practice. After introducing the function constraint and arguing that morality has an underlying point or function, I suggest that longtermism (MacAskill 2022) exemplifies a hubristic moral view. If my argument is persuasive, a broader conclusion follows: the content of moral norms is constrained by morality’s function. As a result, normative ethicists must adhere to the function constraint to avoid moral hubris in their theories. Finally, I suggest that utilitarian views are more prone to moral hubris than Kantian or contractualist perspectives.