“Consider a culture in which people believe it is wrong to eat cows. This may even be a poor culture, in which there is not enough food; still, the cows are not to be touched. Such a society would appear to have values very different from our own. But does it? We have not yet asked why these people will not eat cows. Suppose it is because they believe that after death the souls of humans inhabit the bodies of animals, especially cows, so that a cow may be someone’s grandmother. Now do we want to say that their values are different from ours? No; the difference lies elsewhere. The difference is in our belief systems, not in our values. We agree that we shouldn’t eat Grandma; we simply disagree about whether the cow is (or could be) Grandma!”

The Elements of Moral Philosophy by James Rachels