Or they simply judge actions on the basis of consequences or consensus. All these methods have their origin in man himself. Emotions buzz and fade. Reason may fail or start from flawed premises. Conscience can be blunted or oversensitive.
Consequences are often difficult to judge.
Consensus is subject to prejudice and perversion. But surely each person has to find the truth that's right for them. Our source of values is divine revelation, not human intuition. God has spoken clearly in history and that is our benchmark. Next, the Christian mind has a different view of humanity.