Ayer’s emotivism is concerned with identifying the specific “moral” feelings that are being expressed, as distinct from other judgments of value. He writes:
In adding that this action is wrong, I am not making any further statement about it. I am simply evincing my moral disapproval about it. It is as if I had said, “You stole that money,” in a peculiar tone of horror, or written with the addition of some special exclamation marks. (emphases added)
But he fails to describe the relevant properties of the “moral” feelings. Here is an attempt to do just this; as Kivy writes:
The direct purpose of ethical argumentation is implied in the exhortative moment of moral value terms: what the late Charles L. Stevenson called their “quasi-imperative” part. These terms evince our approval; but they also urge our attitudes upon others. “I approve; do so as well,” was Stevenson’s rough analysis of “good.”
This idea does pick up on something real. All virtues are intersubjective; but other-regarding virtues are objective, being principles of natural law and between different human persons; whereas self-regarding virtues are subjective, justifying one’s own personal trinity within, being about how well one conforms to his own moral ideals.
So, “murder is wrong,” if truth-apt, and if true, then true for all people. If I am convinced that murder is wrong, I might indeed be interested in another person’s moral improvement, as well, perhaps out of charity, and so desire that he, too, realize that murder is wrong.
But for emotivists, “murder is wrong” is not truth-apt and has no truth value. How then am I to persuade you that murder is wrong? Suppose we both agree on the facts of a particular murder: the butler did kill his master with a blunt weapon for money. I then, bleah, vomit my emotions onto you. What reason do you have to imitate me from now on? I can’t think of any. You may have your own emotions to vomit quite pleasurably. If you are content, what can I do to change your ways? Nothing, and this version of emotivism fails.
I mean, seriously, when a philosopher is doing any work in normative ethics, is he saying: “Alright people, I’m about to vomit my emotions on you. Prepare yourselves; hold on to your handrails and brace for impact, because this baby is coming out full blast. AAA-aaahhh!!”