Philosophers since ancient time have pondered how we can know whether moral claims are true or false. Aristotle (386-322 B.C.) called attention to this concern in his Niconachean Ethics: "Now fine and just actions admit of much variety and fiuctuation of poinion, so that they may be thought to exist only by convention, and not by nature." The first half of the twentieth century witnessed widespread skepticism concerning the possibility of moral knowledge.
Indeed, some argued that moral statements lacked cognitive content altogether, because they were not susceptible to empirical verification. The British philosopher A. J. Ayer, for example, contended in his seminal work, Language, Truth, and Logic (1936), that "sentences which simply express moral judgements do not say anyting. They are pure expressions of feeling and as such do not come under the category of truth and falsehood. They are unverifiable for the same reason as a cry of pain or a word of command is unverifiable--because they do not express genuine propositions."
- Dasvid copp Realist-Expressivism: A Neglected Option for
Moral Realism
- Shelly kagan Thinking about Cases
- George sher But I Could Be Wrong
- Brian letter Moral Facts and Best Explanations
- Philip pettit Two Sources of Morality
- Stephen darwall "Because I Want It"
- David O. brink Realism, Naturalism, and Moral
Semantics
,etc.