How did Bernard Williams distinguish moral judgments from scientific descriptions of the external world?

Bernard Williams distinguished moral judgments from scientific descriptions by rejecting the idea that ethics should mirror the "absolute conception" of reality found in the physical sciences.1

In science, the goal is to describe the world as it exists independently of any human perspective, aiming for a single, objective truth. Conversely, Williams argued that moral judgments do not attempt to represent external entities or structures in the world. He contended that while scientific objectivity involves correcting for human biases to reach a universal view, applying this same ambition to ethics is fundamentally misguided.1

For Williams, moral judgments are practical, concerning how people should live and act, and must be rooted in an individual's existing motives—what he termed "internal" reasons. He believed that attempting to transcend one's personal perspective to achieve an impersonal, universal moral standard is absurd and risks self-deception. Instead of seeking timeless, objective truths, he argued that ethical understanding is often local, historically contingent, and deeply tied to the human point of view.1