It seems that in order to claim anything is intrinsically wrong, one must assert

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It seems that in order to claim anything is intrinsically wrong, one must assert that some specific thing, be it happiness, duty, eudaimonia or something else, has intrinsic value. I cannot see, however, what logical process can lead one to this conclusion from a materialist perspective. If all that exists is matter, then what kind of property would 'value' be? If happiness, for example, is simply a mental state, no different from sadness or pain, then how can it have the property of 'value', and what kind of property might this be?