A man's interest in the world is only the overflow from his interest in himself. When you are a child your vessel is not yet full;so you care for nothing but your own affairs. When you grow up, your vessel overflows; and you are a politician, a philosopher, or an explorer and adventurer. In old age the vessel dries up: there is no overflow: you are a child again.
It is not the number of years we have behind us, but the number we have before us, that makes us careful and responsible and determined to find out the truth about everything.