In 1977 he published Rich Christians in an Age of Hunger, a hurricane of a book, selling 350,000 copies. It examines how western Christians live in luxury, while throughout the world millions die in poverty. He called on Christians not only to give more, but to develop a simpler lifestyle, so they could give not the minority but the majority of their income away.

His model for this was John Wesley. Sider points out how Wesley gave away most of what he earned, ate basic food and wore cheap clothes, declaring, "If I leave behind me £10 pounds, you and all mankind bear witness against me that I lived and died a thief and a robber."

Sider notes that Wesley preached what he practised. This was not just his personal lifestyle, but something he expected of all Methodists. Christians should give away all but "the plain necessaries of life" – wholesome food, clean clothes and enough to continue their business. Anyone who keeps more "lives in open, habitual denial of the Lord".

Sider offers many guidelines for Christians who want to follow Wesley's lead. For example, living in community to share resources, and quitting stuff that we buy for status or fashion. He also recommends the "graduated tithe": instead of Christians giving one-tenth of their money, they should give a tenth of the the first $8000 (in 1977 money), then 15% of the next $1000, 20% of the next $1000, etc.

It is a passionate summons, very much in the spirit of John Wesley.

Says Sider: "We have become ensnared in unprecedented material luxury. Advertising constantly convinces us that we really need one unnecessary luxury after another. The standard of living is the God of the 21st-century westerner, and the ad man is his prophet."

Click here to order your copy of Rich Christians in an Age of Hunger.