We watch, we experience, we learn, we read, we ask around, we interact.
Same as with any other thing. If I stole your wallet you'd immediately knew it wasn't right, wouldn't you?
>I don't think that principles are much more than oral tradition.
Well, I don't think oral tradition is not a good basis to base principles on. It implies historical experience, communal values, the test of time, and so on.
It might not be perfect, but then again, it need not be.
I agree that oral tradition is not a good basis to base principles on, lol. Welcome to my world.
"What is right" and "what is wrong" are good questions - ask yourself that repeatedly, over years, and you can find your principles too. "Why is X right/wrong?" are also helpful :)
It is subjective. I said that from the beginning. The value of strong principles is being able to make decisions with intent and confidence.
Unless you consult an RNG for every decision, you still live by a set of principles... emergent, unexplored, uninformed ones, but principles nonetheless. Why do you work? Why do you do that work? Heck, why do you do laundry?