The most famous and relevant line that deals with the concept of a man as a child is: "What a piece of work is a man! How noble in reason, how infinite in faculty! In form and moving how express and admirable! In action how like an angel, in apprehension how like a god! The beauty of the world, the paragon of animals—and yet, to me, what is this quintessence of dust?"
This passage from Act II, Scene II, highlights the duality of human nature: we are both magnificent and flawed, capable of great things but also prone to weakness and folly.