The interest of Augustine in the operations of the human mind was revealed in his spiritual unease and his questioning of himself.
This is seen in his Confessions, and in his images of the Trinity in his other great major work, De Trinitate ("On the Trinity").
This had a profound influence on the psychological theories of medieval scholars.
Through the medieval period and until the reintroduction of the ideas of Aristotle, the thoughts of Augustine on psychology were the only accepted ones.
Augustine supported the view of Plato that the soul is immaterial and would never die, and that the body is material and mortal.
He believed that knowledge was obtained through an awareness of self, and not from sensory impressions.
He thought of the mind as a unity with independent facilities (reason, memory, will and imagination) and originated what is now known as faculty psychology.
He anticipated by many centuries the French philosopher, Rene Descartes, concerning the proof of self-existence: to doubt is to think, to think is to exist.
The personality of Augustine himself was both complex and profound.
He was a person who thought rather than a scholar who possessed a metaphysical, speculative mind.
Very possibly his emotional and psycho-social maturation did not keep pace with his mental development.
This might go some way to explaining psychologically his need for friendship, some of the bad behaviour of his youth, and even his choice of community life after his conversion.
The observations and descriptions by Augustine about human motives and emotions, his depth analyses of will and thought in their interaction, and his exploration of the inner nature of the human self have established one of the main traditions in European conceptions of human nature, even down to our own days.
In psychology, it is from Augustine that Europeans derived their sense of society, individuality and personal rights within the social order.
His view on the role of history in humanity, and indeed his world view generally, dominated the thought about these matters in the Middle Ages.
Certainly, it is impossible to describe the Middle Ages (and even subsequent centuries) fairly without giving Augustine a prime position.
