SOUL AND MIND Soul, from which they have originated and to which they return (3 4) We shall learn more about this World-Soul in Chapter 9, when we come to discuss Plotinus’ theology One of those who learnt most from Plotinus’ speculations was the young Augustine His own original contribution to philosophy of mind, however, is to be found in his writing on freedom In his de Libero Arbitrio, written in the year of his conversion to Christianity, he defends a form of libertarianism that diVers both from the compatibilism we saw in an earlier chapter when considering Chrysippus, and from the predestinarianism for which the later, Christian, Augustine is notorious In the third book the question is raised whether the soul sins by necessity We have to distinguish, we are told, three senses of ‘necessity’: nature, certainty, and compulsion Nature and compulsion are incompatible with voluntariness, and only voluntary acts are blameable If a sinner sins by nature or by compulsion, the sin is not voluntary But certainty is compatible with voluntariness: it may be certain that X will sin, and yet X will sin voluntarily and will rightly be blamed St Augustine in his study (Vittorio Carpaccio, S Giorgio, Venice) 254