Viewed in its entirety, moral philosophizing, and the moral behavior of people throughout history, presents a curious puzzle. On the one hand, interpersonal duties display a remarkably stable core content: morality the world over enjoins people to keep their word; refrain from violence, theft and cheating; and help those in need. On the other hand, the asserted motives that drive people’s moral actions evince a dazzling diversity: from empathy or sympathy, to practical or prudential reason, to custom and honor, cultural identity, excellence and independence, faith and spirituality, narrative and beauty, and more besides. I term this twin phenomenon—a core of fixed moral duties driven by diverse motives—“moral motive pluralism.” In this article, I marshal evidence to show the prevalence of the phenomenon. Contrary to widespread assumptions, across generations and cultures, diverse motives drive different people to perform their moral duties. But despite this diversity, each different motive impels conscientious compliance with the same core moral duties. I argue this phenomenon undermines key types of evidence commonly employed to justify popular moral philosophies, and provides us with reason to seriously consider certain sorts of ethical theories—especially “functionalist” accounts of morality.