William of Ockham's Razor
A philosopher and a theologian who lived in the 14th century, William of Ockham made a long-lasting contribution to scientific thought.
To those who claimed that all knowledge must be based on Scripture, William pointed to God's world, and asserted that God was not arbitrary, and the laws of nature were reliable. To understand that world William proposed the law still known as Ockham's Razor. This is the idea that the simplest explanation with the least assumptions is probably the right one. Ockham's Razor underpins western science, and has remained sharp all these years.
An English Franciscan whose feast day is celebrated in the Anglican Communion today, William travelled from England to Avignon to defend his ideas and to advocate simplicity of life for the followers of Christ. This Christian notion irritated the schismatic Pope ruling in Avignon, and William fled to Munich.
For the next two decades he advocated a political and social settlement that has been adopted in the West. Like a razor, the settlement has two sides - political power is vested in a secular state, and spiritual power is vested in the church. It is not a perfect settlement. It does not always work. And spiritual power does not reside only in the church. But it has allowed for spiritual and political freedom.