The Is-Ought Problem

No descriptive claim can entail a prescriptive claim.

Prescriptive claims contain normative content ("ought") that is not present in any descriptive claim ("is"). A valid deduction can rearrange and combine the content of its premises, but cannot introduce content that isn't there. Since no descriptive claim contains "ought," no deduction from purely descriptive premises can yield an "ought" conclusion.

Example

"People suffer when lied to" is a descriptive claim. "You ought not to lie" is a prescriptive claim.

The first does not entail the second. To connect them requires an additional premise: "You ought not to cause suffering." This premise is itself prescriptive, not derived from any description.

The same holds for any descriptive-to-prescriptive inference. "Aggression causes harm" does not entail "One ought not to aggress." Every attempt to derive "ought" from "is" contains a hidden prescriptive premise.

2025-10-08 Aaron Brinton