This is not a book about the Five Ways to prove God’s existence as developed by Saint Thomas Aquinas.  There is a similarity in the methods involved by Feser, a well-known Christian philosopher who hearkens back to the truths and validity of Scholasticism, summarised and canonised by Saint Thomas Aquinas.  Two of the proofs are found in Aquinas and three are related but not explicitly given by the great Catholic theologian and philosopher.  These arguments used by Feser are inspired and discussed by Aristotle, Plotinus, Augustine, Aquinas and Leibniz.  Feser accepts the Aristotleian proof of God’s existence but does not use Aristotle’s own defence but elaborates using Aristotelian logic to develop a related but deeper proof of God’s existence.  He does something similar with the aforementioned five philosophers. 

Feser uses these five philosophers, devoting a chapter to each.  He presents the informal statement of an argument in two phases, arguing initially for the existence of something defined concretely such as ‘an uncaused cause of the existence of things’ and a second phase ascribing the description to key divine attributes, including unity, eternity, immateriality and omnipotence.  Feser attempts to avoid unnecessary technical detail and vague digressions. 

An example is Chapter 1 on Aristotle.  This begins with the fact that there is real change in the world.  Change is the actualisation of change.  No potential would be actualised unless there is something which can actualise the change, without itself being actualised.  This means there must be a pure ‘actualizer’ an unmoved mover, as Aristotle stated about God.  Aristotle discusses this logic in book 8 of his Physics and book 12 of his Metaphysics.  Later Aristotelians such as Aquinas developed their own versions including the Saint’s own ‘5 ways’ to summarise the key arguments using somewhat archaic ancient notions about the movement of heavenly spheres.  Feser utilises the modern conceptions of motion and energy to defend Aristotle’s system. 

Each chapter supports the 5 proofs of God’s existence by looking at Neo-Platonism (the One, divine simplicity and perfection in the divine mind), Augustinianism universals (humanness, rejection of Plato’s third realm of forms, a systemic presentation based on Leibniz), Thomistic proof of God’s existence (distinction between essence or what the thing is, or its existence the fact it exists), elaborating Aquinas’ ‘On Being and Essence’ the paradigmatic argument for God’s existence.  Feser’s last chapter is the rationalistic proof of God’s existence using the principle of sufficient reason.  The last two chapters deal with the rationality of conservation in which the world could not exist without God sustaining it; and the addressing of various criticism of natural theology. 

The book is the most comprehensive modern defence, reaching back through Neo-Scholasticism to medieval scholasticism and pagan philosophers and scientists.  Since the age of the poorly named ‘Enlightenment’ these proofs, arguments and science are simply ignored.  The poverty of modern philosophy is that there is no debate with the truths and proofs from the past.  They are simply ignored or debased and dismissed. There is much to admire in the line of Neo-Scholasticism and the recrudescence of ancient verities and knowledge.  This is probably the best one volume demonstration of God’s existence using millennia of knowledge.