Francis of Assisi was a Catholic deacon and the founder of the Order of Friars Minor, more commonly known as the Franciscans.

Francis heard a sermon that changed his life. The sermon was about Matthew 10:9, in which Christ tells his followers that they should go forth and proclaim that the Kingdom of Heaven was upon them, that they should take no money with them, nor even a walking stick or shoes for the road. Francis was inspired to devote himself to a life of poverty.

Francis's attitude towards the natural world, while poetically expressed, was conventionally Christian. He believed that the world was created good and beautiful by God but suffers a need for redemption because of the primordial sin of man. He preached to man and beast the universal ability and duty of all creatures to praise God (a common theme in the Psalms) and the duty of men to protect and enjoy nature as both the stewards of God's creation and as creatures ourselves.