Why be good?
People have spilled a lot of ink on this one. And there are countless bad arguments (“god commands it!” or “society says so!”) as well as more good arguments than you might guess.
Some are pretty simple – and while they aren’t full, rigorous systematic answers to the problem of “why” in morality, they’re useful heuristics for getting through life.
You might consider being good, for instance, because you want to be able to see the good in the other humans you interact with.
It’s pretty obvious that we project our own worst attributes onto others. As C.S. Lewis noted regarding vices like pride:
“. . .the more we have it ourselves, the more we dislike it in others.”
The same goes for any of the traditional vices: greed tends to cast the world in a greedy light, hate in hateful light, and so on. Your experience of the world will be cast in the light you create.*
Fortunately, you’ll have also noticed that you tend to also see the virtues in others (courage, generosity, honesty, etc.) when you have been virtuous yourself. And no one can deny that it’s strongly in our self-interest to hope for these things in our fellow humans and in the world we live in.
Remember when you helped that poor person, visited that sick person, comforted that lonely person? I doubt you went out afterwards seeing more of the badness in humanity and the world. We control our experience of life and program it with our actions, so we benefit by choosing to cast clear light.
Again, not a full answer by any means to the philosophical question of morality. But then, maybe the question is not as complicated as the philosophers think. Self-interest tends to justify itself, and there is plenty of self-interest on the side of the virtues.