More than two thousand years ago the Greek philosopher Democritus wrote, “Raising children is an uncertain thing; success is reached only after a life of battle and worry.” Not much has changed since then. The parenting shelf in the bookstore is filled with thick volumes of advice. For decades anxious fathers and mothers have embraced the latest theories, from Dr. Spock’s Baby and Child Care to Amy Chua’s Battle Hymn of the Tiger Mother, in an effort to raise happy, well-adjusted children.