Citation Hunt

The Wikipedia snippet below is not backed by a reliable source. Can you find one?

Click I got this! to go to Wikipedia and fix the snippet, or Next! to see another one. Good luck!

In page Philippa Foot:

"

Though non-cognitivism may be traced back to Hume's Is–ought problem, its most explicit formulations are found in the works of A. J. Ayer, C. L. Stevenson, and R. M. Hare, who focused on abstract or "thin" ethical concepts such as good/bad and right/wrong. They argued that moral judgments do not express propositions, i.e., that they are not truth-apt, but express emotions or imperatives. Thus, fact and value are independent of each other.[citation needed]