Almost everyone acts and justifies their actions based on the assumption that morality is worth following. The moral foundations people use to justify their actions and with which they plan out courses of action differ, but fundamentally most people have the intuition that some actions are right and others wrong.
Where this runs into trouble is when people try to convince other people that their own morality is correct and the other person’s is wrong. In doing so, this action assumes that there is some external morality that both people should follow. To many people, though, it seems impossible to derive any moral statement from a fact about the universe.
If morality is not objective — if it does not follow from a fact about the universe — another option is that it is subjective. In support of that, we can see that some parts of human morality appear to reflect the nature of humanity, and our fundamental moral beliefs can often be traced causally back to some step in human evolution. But at the same time many people have the intuition that, even if humans or human society had evolved differently, true morality would be the same.
Can we reconcile these two competing intuitions, or must one be thrown out? Is morality fundamentally tied to human beliefs about it? Is there an objective morality?