Some maintain that moral judgments are just opinions.
The evidence for this is the fact that people disagree with each other about the right thing to do.
The disagreement is not the only relevant evidence, however. It is also necessary to explain why morality is universal and to explain why it is more effective to say that something is wrong than it is to say that you do not like it. If morality were just opinions, we would not need and probably would not have a special moral vocabulary. If morality were just opinions, its effectiveness when it comes to influencing others would be inexplicable.
The relativist hypothesis is that different moral codes and opinions are all basic rather than explicable in terms of underlying factors.
But there could still be differences in moral codes and moral opinions even if the basis of morality was shared by all moral agents.
Two causes of differences would be ignorance and error. Indeed, as we saw in the fourth paragraph in the section called “Evidence,” there are enough relevant causal factors that the differences are inevitable.
In view of all the relevant observations and the alternative possible explanations, it is irrational to be a relativist.
Factors like ignorance and error can also distort our intuitions.