As you might already know, many religions require adherents to donate a fixed portion their yearly income, usually 10 percent, to the religious organization to which they belong. Much of that money goes toward funding explicitly religious services, but some does go toward charities that are doing good work. Which raises the question: one need not believe in the supernatural to help others, so why don’t we all try to give 10 percent? This radical idea is the driving point behind a new British campaign called Giving What We Can, which asks people to donate 10 percent of their yearly earnings to well-rated charities. Here is the pledge taken by volunteers: I recognise that I can use part of my income to do a…