Are there knowable 'moral truths'

A matter of  debate in contemporary meta-ethics whether there are knowable moral truths

Our belief in equal human dignity, for example, along with derivative beliefs about the wrongness of slavery or rape, might be sufficiently explained by our having grasped the moral truth that human beings have such dignity and so should not be treated as “mere means” 

 Similarly, the belief that we have moral obligations to mitigate suffering even among distant strangers might be explained at least in part by our having grasped the moral fact that pointless suffering is intrinsically bad and that this gives us good reason to mitigate it where we can.

Instead, a significant amount of moral judgment and behavior may be the result of gaining moral knowledge, rather than just reflecting the causal conditioning of evolution. This might apply even to universally held moral beliefs or distinctions, which are often cited as evidence of an evolved “universal moral grammar” 

The best explanation for deeply reflective moral judgments may look quite different from the explanation for unreflective psychological dispositions we share with other primates, and there may be mixed explanations for much that lies in between