Biblical truths are reflected in everyday life. So, stealing and murder and lying aren’t wrong because the Bible says so. Rather, the Bible says stealing and murder and lying are wrong because they are wrong. They were always wrong, and the Bible testifies to that timeless Truth that predates the Bible itself.... Thus the wrongness of sexual immorality should also be as self-evident as the wrongness of stealing or murder.
David Kupelian, How Evil Works, p.43