In the context of the moral realism vs. moral subjectivism and theism vs. atheism debates the question of moral semantics is often raised: How do we define goodness? Some are under the mistaken impression that if we cannot define goodness (a question of moral semantics) then we cannot claim to know goodness exists (a question of moral ontology) or identify what is good (a question of moral epistemology).
I do not want to focus on whether it is possible to provide an adequate account of moral semantics, but rather to point out that even if we are unable to do so, it does not follow that there are no objective moral goods or that we are incapable of knowing them. Greg Koukl illustrates this point beautifully. He notes how our experience of goodness is similar to our experience of color. We recognize color as color when we see it. If someone were to ask us how we know what green is, we would respond, “I just see it.” We don’t need to define green to know it when we encounter it. Similarly, we do not need to define goodness to know that we have encountered it. God has given us moral intuitions to recognize good and discern between good and evil.
Thinking to Believe 