It is important to understand Augustine’s teaching on the ultimate good (summun bonum) because it is the source of many doctrines in modern Christianity. Without this key teaching, many of the negative attributes of God may have never solidified. It then is important to understand what this teaching entails and what implications it imparted to Christian teachings. Only then can we re-evaluate our own understanding of Christianity in light of possible Platonic contamination.
During the time of Augustine there were two main competing views on the nature of “good”. Platonism stressed that the “the good” (a synonym for “god” in their vocabulary) was an unchangeable perfection (similar to Plato’s Theory of Forms). To the Platonist, god was an anti-concept that could not be compared with material being in any real sense. The “good” of the Platonic god, was not “good” that humans could understand. It was an ultimate ideal state. Any “good” in the material world was merely shadows of that unchanging perfection. In fact, material world was less than ideal and any good philosopher would dedicate their life to reaching this ideal state (through meditation and abstaining for things of the flesh). Augustine adopted these ideas directly from Plato and incorporated them into his primary teachings:
The highest good, than which there is no higher, is God, and consequently He is unchangeable good, hence truly eternal and truly immortal. All other good things are only from Him, not of Him. For what is of Him, is Himself. And consequently if He alone is unchangeable, all things that He has made, because He has made them out of nothing, are changeable.
Notice that Augustine contrasts that which is mutable and created against that which is immutable and uncreated. The created was a shadow version of the perfect. Augustine explains all this in his book On the Nature of Good. In this writing he tried to convince his main opponents that this “good” of Platonism was true while their dualistic thinking was false. They were called the Manicheans (followers of Mani), and Augustine had been a hearer for them for approximately 9 years.
The Manicheans were dualistic. They represented the other main thought on the nature of “good” during the time of Augustine. Whereas the Platonists saw evil as the departure from the good, the Manicheans saw good and evil as two competing powers. The good could not be contaminated by the evil and could not touch it. The “good” was not the cause of everything (as it was for the Platonists), because they claimed that evil could not be caused by the good. Modern Manicheanism might be found in Christians who claim everything evil is caused by the devil (as if the devil was an equal but opposite force to God).
Augustine argued that although God was the cause of all things and the ultimate good (the summun bonum), that free will was the reason for evil. This allowed him to say that God had ultimate power, yet evil could exist. Because we do not have have his opponent’s response, we might be safe to assume they were less than impressed.
It is important to note, the Bible does not speak in these terms (of the Platonists or the Manicheans). The Bible does not rattle on for pages about intangible concepts that bare no relation to God’s creation. Augustine specifically learned his teaching straight from Plotinus, and literally (and admittedly) reinterpreted the Old Testament to fit this Platonic theology.