William of Ockham gave philosophy its most famous rule: do not multiply entities beyond necessity. He also spent years on the run from the Pope, excommunicated for arguing that the church had no right to own property.

This episode traces how a Franciscan friar from a Surrey village became one of the most influential logicians of the Middle Ages and a political fugitive whose ideas about poverty nearly toppled papal authority.

• What Occam’s Razor actually says and how it has been misused
• His nominalist philosophy and why it threatened church doctrine
• The flight from Avignon and his alliance with Emperor Louis IV
• How his political writings laid groundwork for the separation of church and state