IN 1693 the philosopher John Locke warned that children should not be given too much “unwholesome fruit” to eat. Three centuries later, misguided ideas about child-rearing are still rife. Many parents fret that their offspring will die unless ceaselessly watched. In America the law can be equally paranoid. In South Carolina this month Debra Harrell was jailed for letting her nine-year-old daughter play in a park unsupervised. The child, who had a mobile phone and had not been harmed in any way, was briefly taken into custody of the social services.