Plato (428 BC – 348 BC)

In Plato’s ontology, the good is the ultimate principle of a reality split into two irreconcilable domains: the spiritual and its shadow, the material. The first to put forth the idea of knowledge as justified true belief, Plato states that the processual and unstable world of material phenomena merely allows for opinions, whereas the realm of non-sensible and immutable forms (intelligible ideas) can offer pure knowledge. It is only reason which can ensure a person’s inner harmony through the control it should exert over will and desires. Thus, will can only manifest freely under the influence of knowledge of the good and of the truth.