When I lie, when I hurt someone's feelings, when I go against a promise, things I strain to avoid but invariably fail to do, I feel bad. A sense of unfairness, a sense that I have done wrong, washes over me. It gnaws it way into my mind, it burrows into my thoughts and eats. It feasts. It holds lavish festivals of gorging upon copious amounts of guilt. It is my conscience and it lives well.
We humans have devloped social codes of conduct and I have been bred with my own flavour of right and wrong. My parents instilled many qualities in me, to many of which I'm sure to be oblivious, and with that I have developed my own sense of fairness and justice, my little code of honour that I adhere to as strongly as possible. My ability to self-justify is as developed as yours so I am quite aware of my guaranteed hypocrisy. My actions can't possibly align with my beliefs all the time. I'll settle for 25% of the time. I sleep 1/3 of the time, so perhaps I should aim higher?
What is equally certain is that I have a sense of right and wrong. Some people practice zero-impact camping, where they leave no impact upon the environment in whch they visit for a little tent pitching. Obviously, you can't have zero impact but you can try to minimize that. I would like to live a zero-impact life. I won't even come close. Not by a long shot but I can try to minimize my personal environmental footprint. It makes me feel ill when I knowingly violate that personal belief but I usually don't think about it until afterwards, or I manage to convince myself to indulge.
These personal crimes do not tickle the back of my brain. They marinate my mind in a searing sauce of self-loathing. I cannot violate the laws of nature but I can and do readily commit sins against my own codes of behaviour, my own definitions of right and wrong. The orbit of Mars will not be altered by my guilt. Fermat's Last Theorem is still solvable even if I trash every belief I have in a ten minute binge. The universe cares not one whit about my definitions of right and wrong. I, and I alone, am responsible for my actions and the ascription of "good" or "bad" to them.
When people talk about there being an absolute right, it seems unlikely to me. There certainly is an absolute law of gravity. I can give you pretty quick example if we ever meet atop a tall building. The absolute wrong seems to me to be the ability to travel backwards in time, or some violation of the laws of nature. Absolute morality in terms of behaviour is not looking at question correctly.
Our minds are conditioned to believe what is right is also what is good for the community. Our survival as a species requires a built-in motive force to prevent us from acting against the common good. This is our conscience. We have developed social codes imprinted via both nature and nurture that allow human society to function. The scale of our society has always been growing so these codes have proved flexible enough to allow their modifcation over time. Witness the ever-evolving role of the female in society. We forbid murder, and our consciences, in proper working ordrer, should not permit us to commit it. We know how bad we feel when we transgress in minor ways and we are taught that even bigger violations bring even bigger pains. Small fire hurt, big fire hurt lot.
So our consciences act not only after the fact but also in a pro-active manner to prevent anarchy from arising in society. We don't need the Minority Report. We already have an evolutionary appendage that prevents all sorts of "bad" acts (ie: destructive to society and the individual), our good ol' conscience.
Unfortunately, I can work around my conscience, often in ways I'm not even aware of. And you can, too. We all do it, daily. Comforting, isn't it?