Global progress is hard. Efforts to eradicate polio (incurable but prevented by simple oral vaccine) are foundering in countries like Pakistan, Nigeria and the, ahem, Democratic Republic of Congo.The oldest human rights movement is the anti-slavery movement dating from the 18th century. There are more slaves now than there were when the movement was founded.The prevention of war, the abolition of nuclear weapons, control of carbon emissions, Millennium Development Goals: it’s easy to come up with grand global initiatives. Almost none of them succeed, though smallpox, thankfully, has been eradicated.Lesson: we can and must fight evils like slavery and disease. But those who think they’ve got a magic bullet to end some ancient scourge are almost always wrong — and clueless do-gooders often make things worse.