A student told me that he doubted the reality of good and right, wrong and evil, because they are “abstract” qualities. I mention the anecdote because I hear this sort of thing often (and also for penance, because long ago I used to say things like that myself).
Now he wouldn’t have doubted the reality of odd and even, of important and unimportant, or of old and new -- and those are abstract qualities too, aren’t they?
Perhaps what he really meant was that good and right can’t be measured by the senses. But those other qualities can’t be measured by the senses either; an odd number of apples isn’t a different weight or color than an even one. Importance doesn’t feel warm, and an old poem isn’t hard to the touch. Such qualities are perceived by the mind. And so are good and right, wrong and evil.
Why then does the skeptic trust in the reality of those “abstract” qualities, but not in the reality of moral qualities? It is suspiciously arbitrary.