Let me paraphrase this slightly to get at the kernels of meaning:
- A system of morality based on relative emotional values is illusion. It is thoroughly vulgar with nothing sound and nothing true.
What Socrates is claiming is that when emotionalism is the foundation of moral choices (if it makes you emotionally happy or excited, it is right and good), then the moral choice is vulgar. Since vulgarity is the antithesis of morality, then the choice based on emotionalism is not a moral choice.
Further, a so called moral choice of this sort ("so called" because "vulgar" has just proven such choices are not moral choices), based as it is on faulty logical reasoning, is not rationally sound. If a choice or an argument or a supposition is not logically sound, then there is nothing true in it.
The association of emotionalism with moral choice is faulty logical reasoning because emotionality equates with vulgarity; vulgar is the antithesis of moral; therefore emotional is the antithesis of moral. Thus a...
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