The Role of Essentially Ordered Causal Series in Avicenna’s Proof for the Necessary Existent in the Metaphysics of the Salvation

Avicenna's proof for the existence of God (the Necessary Existent) in the Metaphysics of the Salvation relies on the claim that every possible existent shares a common cause. I argue that Avicenna has good reason to hold this claim given that he thinks that (1) every essentially ordered causal series originates in a first, common cause and that (2) every possible existent belongs to an essentially ordered series. Showing Avicenna's commitment to 1 and 2 allows me to respond to Herbert Davidson's and Richard Swinburne's claim that Avicenna's proof for the Necessary Existent is incomplete and fallacious