Four hours later... a breakthrough emerges to answer the teenager.
Today may see the birth of a mass-murderer.
Good. Now that I have your attention, let us begin.
I've just come away from a chat and realized that the fuel behind my moral compass possibly doesn't exist (not going to discuss it, is boring). And so I need to create a new compass, from the ground up.
There are three stages to this:
alpha: I must realize my own power. If I realize that I can lie to people, that I can be deceitful, that I can sleep around, and so forth - if I realize that I can do all that which I hate and despise, then I'm well on my way. Why? Because knowing that I can do something but choose not to is different to saying that something is wrong when I cannot do it.
It then sounds a bit too much like cowardice - using morals to protect oneself against that which one cannot do. (Nietzsche has much to say about this, I believe. And with greater eloquence and syphilis than me.) It's mentioned in the fable of the Fox and the Grapes.
Another bad analogy would be how states without nukes may passionately scream that using nukes is wrong. Such states do not have nukes; by declaring nuke-use(!) to be wrong, they place pressure on those with nukes not to use them. As a result, they minimize the emasculating effect their lacking nukes places causes them to have. Sour grapes, indeed.
Thus, I need to realize that I have the power (this sounds like a bad Spice Girls single), that I can do bad things and get away with it and so on. I don't have to do all this in reality; I can just do it in my head. It does require some effort, though.
alpha, part two: However, some acts are not only 'bad' in principle; they are also bad from a self-interest practical POV. Lying to friends (or betraying them) is one such thing: if you lie to your friends, they won't trust you. This means that even the most selfish of people will not be able to lie to their friends often and win at life. In contrast, quietly stealing a baby's lollipop in a dark alleyway doesn't have this problem. The baby cannot tell others, the baby cannot do anything, you do not need the baby. There is no negative repercussion upon you (except the baby spitting all over you. Ick.) The only thing that deems such an act wrong is principle, not practicality.
In such a world, if you could steal the baby's lollipop but choose not to, then you know that you find lollipop-stealing to be wrong. (Or you don't like lollipops. In which case you are a freak - everyone likes lollipops. I like those candy-canes too. Coca-cola flavour, please!)
Thus, living with pure self-interest can mean that you behave nicely to your friends and colleagues. It just means that you can also steal babies' lollipops.
beta: It's okay to hold whatever morals I want.
If, as alpha says, I'm free (and powerful enough) to do whatever I want, then what I do end up holding must be the real me. In the absence of religion and with enough fooling-of-peers, I could do 'bad acts' without indirect repercussions (as opposed to direct ones arising from the act itself. See the betrayal-vs-lollipop discussion earlier.)
It is only in such a state - having freedom and the power to do what I want - that the choice of what actions I will and will not undertake reveal what my true morals are.
And only then will I be secure in which way my moral compass points.
ETA: Just one problem: I love beauty; especially that of abstract ideas. This means that I will find some actions that may benefit my 'self-interest' to be objectionable solely because they lack beauty. But then I realize, faintly, that self-interest tends to be measured as that which benefits us tangibly. Money, power, and career aren't the only measures of a life. If I love beauty, then if I do an act which leaves me penniless and powerless but makes me think: "Ahh, beautiful", then that need not be against my self-interest. Self-interest can be more than just money or power. And I shouldn't always fight that which I find beautiful. I should just have an open mind (that is most difficult!).
More may appear in this journal as I continue such cogitations.
Now that I am no longer a powerless teenager, I need to create a new (and flexible) moral compass for myself.