A Treatise on God as First Principle

A short, tightly argued treatise on natural theology, among Scotus's last works, drawing on his lectures on the Sentences. It opens and closes with prayer, and proceeds like a work of geometry, by numbered conclusions. Chapters 1 and 2 set out the kinds of essential order: one thing can be prior to another in eminence or in dependence, and dependence covers the four causes. Chapter 3 proves a triple primacy. Starting not from what actually exists but from what is possible, Scotus argues that some effect can be produced, that an infinite series of essentially ordered causes is impossible, and so that a first efficient cause is possible; since such a cause could not be caused by anything else, it actually exists. Parallel arguments give a first final cause and a most eminent being, and the three are shown to be one and the same nature. Chapter 4 argues that this first being is simple, intelligent, willing, infinite and unique.

It contains one of the most rigorous medieval proofs of God's existence, including an early argument from possibility, and shows Scotus's careful method in a compact form.