If parents are the fixed stars in the child's universe, the vaguely understood, distant but constant celestial spheres, siblings are the dazzling, sometimes scorching comets whizzing nearby.

Samuel Johnson called it the vanity of human wishes, and Buddhists talk about the endless cycle of desire. Social psychologists say we get trapped on a hedonic treadmill. What they all mean is that we wish, plan and work for things that we think will make us happy, but when we finally get them, we aren't nearly as happy as we thought we'd be.

Siblings are the guarantors that the private childhood world - so unlike the adult world that scientists are only just beginning to understand it - is a fully shared and objective one.

Alison Gopnik Quotes