Arthur C. Clarke said this quote

“ And yet, even while they baffled him, they aroused within his heart a feeling he had never known before. When- which was not often, but sometimes happened- they burst into tears of utter frustration or despair, their tiny disappointments seemed to him more tragic than Man’s long retreat after the loss of his Galactic Empire. That was something too huge and remote for comprehension, but the weeping of a child could pierce one to the heart.Alvin had met love in Diaspar, but now he was learning something equally precious, and without which love itself could never reach its highest fulfillment but must remain forever incomplete. He was learning tenderness. ”