Analytic philosophy
Emotivism

The second is founded on logical positivism and its attitude that unverifiable statements are meaningless. As a result, they avoided normative ethics and instead began meta-ethical investigations into the nature of moral terms, statements, and judgments.

The logical positivists opined that statements about value —including all ethical and aesthetic judgments—are non-cognitive; that is, they cannot be objectively verified or falsified. Instead, the logical positivists adopted an emotivist theory, which was that value judgments expressed the attitude of the speaker. It is also known as the boo/hurrah theory. For example, in this view, saying, "Murder is wrong", is equivalent to saying, "Boo to murder", or saying the word "murder" with a particular tone of disapproval.

While analytic philosophers generally accepted non-cognitivism, emotivism had many deficiencies. It evolved into more sophisticated non-cognitivist theories, such as the expressivism of Charles Stevenson, and the universal prescriptivism of R. M. Hare, which was based on J. L. Austin's philosophy of speech acts.
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