It's really easy to be right with oneself, because if I just indulge my every whim of passion, without conscience, without the external guidance of God's Law which both educates me about right and wrong as well as condemn me because I am, indeed, wrong; then I can do anything and I will always be right--because I am myself, doing whatever I want.
If I have absolutely zero empathy for others, regard no one and nothing as having value other than myself--then I can do anything and be fine with it. That is Selfishness as a "virtue", and I can justify literally anything: lying, stealing, cheating, rape, murder. This is literally the basis, the source, of every and all moral evil in the world.
There must, therefore, be some sort of external control. A law. Even before we talk about God's Law, we can just as easily talk about "natural law", the sort of innate recognition most people have, because we are naturally social creatures who exist in communities with other people, and so we sort of intuitively get that we have to get along--so going around killing people or generally being really nasty isn't fruitful toward the building of human societies where we also have to depend on one another for food, shelter, and protection from hostile forces (perhaps another tribe that is competing with our tribe for the same resources and may consider eliminating us the most efficient way to secure those resources; or perhaps wild animals that are dangerous, or perhaps just the unpredictability of the weather). And so we intuitively get that cooperation is better than going around murdering one another all the time, and as we exist in societies we also then teach our children that it's good to share, that obeying those in authority is usually good, work things out with others by talking rather than fighting, etc. And so societies grow, exist, and sometimes we even do okay for a while.
That's why we have systems of justice in place, rules, which govern human conduct. Because we need an external force to say, "Get along", because even if 9 out of 10 people will prefer to cooperate than murder one another, there's always that 1 person who, for whatever reason, thinks "Hey, that person has food, I'm hungry, I should just take it, and maybe kill them so that they won't be competition in the future when I want food" or something along those lines. So we develop rules of law, systems of justice, and we enforce these systems through organizational efforts like courts and so forth. And, generally, human societies work, more or less, at least for a while.
So on a purely mundane level, "self justification" just doesn't work as a principle, because we have to be "other-justified" we have to do right by one another, in order to survive. That's the foundational principle of all human societies and civilization: We have to get along, and that means treating one another fairly.
But then, when talking about what it means to actually be Righteous or Just, with a capital 'R' or 'J', in that God says, "Do this" or "This is how things ought to be", well now we are talking more than just how to get along but instead talking about a cosmic sense of Justice, well that's where things get even bigger and more serious--and that's where the problem of Sin--and our proclivity of self-justification--is really the heart of the issue. The actual problem with everything in the world actually is ourselves, we're the problem, and self-justification (sin) is the reason we're the problem.
-CryptoLutheran
