道德相对主义 - 维基百科，自由的百科全书

Many people in other times and places thought slavery, for example, acceptable, even good; while most today view it as a great evil. Many writers and thinkers have held that one can justify any number of evils based on subjective or cultural preferences, and that morality requires some universal standard against which to measure ethical judgments. A moral relativist might respond that this criticism is only valid if one already accepts that such acts are indeed fundamentally evil - a position which the moral relativist would deny - and that the objection is therefore nothing other than an uncritical statement that morals are in fact absolute.

However, if it is their society that has, for instance, rejected slavery, they presumably agree that it is wrong, if their position is one of social or cultural moral relativism. This presents a meta-ethical problem in explaining what happens when a society has a collective change of heart. Consider the case of someone who has minority moral views within their society, and yet is vindicated (even relativistically) by future developments. If "right" and "wrong" literally mean "what my society accepts/rejects" then a social moral relativist in a slave-owning society of the past who says "slavery is wrong" is effectively saying "slavery is not approved of by my society", which is false — factually false. Yet, the relativist of the present is committed to agreeing with the relativist of the past, since they both oppose slavery.

The argument was phrased in terms of cultural relativism, but a similar argument applies to subjectivism. It is difficult for a moral subjectivist to claim that they have undergone any personal moral improvement, or that an attitude they used hold was wrong, when it was obviously what they felt was right at the time. For them, there is no external standard to judge against, so while their attitudes change, they cannot be said to improve or decline. It therefore seems that there is a difference in what can be expressed or justified between an objectivist and a relativist, although whether it involves the loss of anything worthwhile is open to debate.

There are also difficulties in putting a boundary upon "society" or "culture" - what people feel to be their social or cultural groupings may well not align with legal and national groupings. The person holding "minority moral views within their society" may consider their "culture" more aligned with that minority than with the larger state or national society which determines what is lawfully acceptable,. This can be seen, for instance, where religious communities within a nation or state hold views on the morality of issues such as abortion or homosexuality which differ from the current legal position on those issues. This flexibility could lead to the objection that cultural moral relativism is "anything goes", since one could find — or found — a society that condones whatever one wishes to do.

The equivalent of such gerrymandering in subjective or personal moral relativism would be for an individual to adopt different principles at different times, which would lead to a very acute form of "anything goes", unless forestalled by a meta-ethical principles that individuals need to be self-consistent. It could be argued that jumping ship in this way is dishonest, but the ethical acceptability of honesty is presumably as relative as anything else if relativism is true.

Some philosophers, for example R. M. Hare (1919 – 2002), argue that moral propositions remain subject to logical rules, notwithstanding the absence of any factual content, including those subject to cultural or religious standards or norms. Thus, for example, they contend that one cannot hold contradictory ethical judgments. This allows for moral discourse with shared standards, notwithstanding the descriptive properties or truth conditions of moral terms. They do not affirm or deny that moral facts exist, only that logic applies to our moral assertions; consequently, they postulate an objective and preferred standard of moral justification, albeit in a very limited sense. Nevertheless, according to Hare, logic shows the error of relativism in one very important sense (see Hare's Sorting out Ethics). Hare and other philosophers also point out that, aside from logical constraints, all systems treat certain moral terms alike in an evaluative sense. This parallels our treatment of other terms such as less or more, which meet with universal understanding and do not depend upon independent standards (for example, one can convert measurements). It applies to good and bad when used in their non-moral sense, too; for example, when we say, "this is a good wrench" or "this is a bad wheel". This evaluative property of certain terms also allows people of different beliefs to have meaningful discussions on moral questions, even though they may disagree about certain "facts".