Kirk: We once were as you are. Spears and arrows. There came a time when our weapons grew faster than our wisdom, and we almost destroyed ourselves. We learned from this to make a rule during all our travels never to cause the same to happen to other worlds... just as a man must grow in his own way and his own time.
Nona: Some men never grow.
Kirk: Perhaps not as fast or in the way another thinks he should. But we're wise enough to know that we are wise enough not to interfere with the way of a man or another world.