There is no evidence for any objective or universal moral values. Put another way, there is no evidence that humans (or other sentient beings) have a duty to behave a certain way based on any facts of or about the universe. There is likewise no evidence that any person has a duty to behave a certain way based on any general beliefs or desires shared by most or all other people. Even if it came to light that all people have certain innate beliefs and desires, it would not follow that every person therefore has a duty or ought to have those beliefs and desires or ought to act on those beliefs and desires.
Even if it could be shown that a certain action, if undertaken by a person, would make everyone in the world infinitely happier, this would still not create an objective duty for that person to undertake that action. It would certainly cause the majority of people to desire that the person in question undertake that action, and to believe that person should or ought to do so, but it would not objectively establish that person should or ought to do so.
I defend moral nihilism, or the view that there are no moral facts and no moral duties, in large part because there is an utter lack of evidence for the opposing view that there are moral facts and duties. Specifically, I defend error theory, or the view that all moral claims are false or at least impossible to prove, but with a caveat: moral claims are only false or impossible to prove to the extent that people intend them to describe objective and/or universal properties of the universe. In cases where moral claims are only intended to convey emotional preferences, command others to act, or describe how one personally intends to act, they do not describe or purport to describe objective or universal facts about the universe and thus are non-cognitive, that is, not capable of determination as true or false, at least not as purported descriptions of objective or universal facts.
As mentioned above, moral nihilism is premised in large part on the fact (or claim) that there is a lack of evidence for the view that there are moral facts and duties inherent in the universe. This means that the grounds traditionally cited as bases for believing in the existence of objective or universal moral facts/truths either lack evidence for their existence or, even if they exist, do not in fact provide a basis for believing in objective or universal moral facts/truths.
An example of a ground often cited as a basis for believing in objective or universal moral truths that lacks evidence for its existence is the existence of a creator god with a knowable will or knowable expectations. While the fact there is something rather than nothing at least suggests that it is possible that an intelligent being created or gave rise to the universe, there is no evidence for a creator god who created a set of norms people ought to follow. Of course, many people believe such a creator god exists, but this does not change the fact that there is no objective, verifiable evidence for that belief. Even if it is possible that an intelligent being created or gave rise to the universe, there is certainly no evidence that this being ever revealed itself or its will to humans. All stories about a god revealing itself or its will to humans are unreliable because they contain elements that depart so much from ordinary human experience that they cannot be trusted, there are countless versions of such stories which contradict each other on key points and there is no known consistent and reliable method for evaluating the truthfulness of their non-historical claims, and most importantly, none of them have been corroborated by any observable evidence in the present.
There is also no evidence that moral norms are simply “out there” in the universe, waiting to be discovered through empirical inquiry. Empirical inquiry can tell us a great deal about how people and other sentient beings do behave, but they tell us nothing about whether the way people and other sentient beings do behave is the way they actually ought to behave. Again, empirical inquiry can provide some insight into how people and other sentient beings believe they ought to behave, but it cannot adjudicate whether those beliefs are valid because it cannot reveal what goals people and other sentient beings ought to have and what means people and other sentient beings ought to use to (attempt to) achieve those goals.
There is also no evidence that intuition, a priori reasoning, or some other “inner” source can reliably tell us how we actually ought to behave. They may tell us how we feel we ought to behave, or which forms of behavior entail hypocrisy or a contradiction. But to the first point, the fact that we feel we ought to behave a certain way does not create an actual duty to behave that way. To the second point, even if a behavior entails hypocrisy or a contradiction, it cannot be established from the available evidence that hypocrisy or contradictory behavior is something which objectively must be or ought to be avoided. That a person does not want to be treated as an end in himself or herself does not establish that the person in question has a duty not to treat others as means to his or her own ends. Besides, the claim that hypocrisy or inconsistency is morally wrong cannot coherently be made unless one has first established the moral standard by which hypocrisy is wrong . Thus, using hypocrisy as the basis of one’s moral standard because one believes hypocrisy is obviously morally wrong is circular reasoning.