10 - Plato's philosophical method in the Republic: the Divided Line (510b–511d)

Summary

Plato's image of the Divided Line has captured the attention of his readers for centuries. Much of this attention has been focussed on the nature of the ontological divisions associated with the four sections of the Line, especially the third. This is as it should be since a number of features of the Line point in the direction of ontology. The initial division of the Line into two parts suggests an ontological focus, as does the subdivision of the first part. But when Plato turns to distinguishing the subsections of the second part, his focus becomes a contrast in methodologies. The method of the third section – which I will call the dianoetic method because it results in dianoia – is distinct from the method of the fourth section of the line – traditionally called the dialectical method, which results in epistēmē or noēsis.

I will maintain that the Divided Line passage suggests that these two methods are distinguished less by their formal features than by the manner in which these two methods are carried out. Both methods employ the formal features of the more general method introduced as early as the Meno and traditionally called the method of hypothesis. When the method of hypothesis is employed incorrectly it can achieve only dianoia and so amounts to the dianoetic method. When the method of hypothesis is employed correctly, one can achieve epistēmē and is engaged in dialectic.