Mormon tells us that we may use the essential opposition between Good and Evil as the means of distinguishing the two, if we understand the purposes of God. The more we understand and believe in the purposes of God, the more we are able to judge if any action leads us towards those purposes or away from them. This becomes a sure judge, as there are only two directions, toward God or away from him. Therefore, if we understand God, we may therefore understand those things that lead toward him.