Nature, more of a stepmother than a mother in several ways, has sown a seed of evil in the hearts of mortals, especially in the more thoughtful men, which makes them dissatisfied with their own lot and envious of another's.
Now I believe I can hear the philosophers protesting that it can only be misery to live in folly, illusion, deception and ignorance, but it isn't -it's human.
What difference is there, do you think, between those in Plato's cave who can only marvel at the shadows and images of various objects, provided they are content and don't know what they miss, and the philosopher who has emerged from the cave and sees the real things?