In the fourth book of the Republic, Plato divides the soul into three parts and explains temperance. By his explanation temperance is the friendship and concord of those parts when the ruling part and two ruled parts are at one in the belief that the reason ought to rule, and don't raise faction against it.How can we understand this explanation?
In the first place, to what extent `at one in the belief' should be understood metaphorically? In the fourth book of the Republic, Plato expalains the structure of the human soul by comparing it with the structure of the republic. Then to what extent the word `at one in the belief' can be applied to the explanation. In other words, to what extent if three parts of the soul have intellectual faculty, the application would be valid?
In the second place, there are views that dividing the soul to three parts, Plato admitted the possibility of incontinence and abandoned the Socratic belief that human virtue is nothing but knowledge. According to Plato's three partition of the soul, what does that possibility mean? And as far as we hold the virtue=knowledge theory, incontinence which includes some kind of knowledge is unaccountable. So Plato introduced the three-partition theory to explain the phenomenon of incontinence. In this interpretation how can we think consistently of the knowledge included in the description of incontinence and the knowledge of the three parts of the soul?