Whenever a person strives, by the help of dialectic, to start in pursuit of every reality by a simple process of reason, independent of all sensuous information - never flinching, until by an act of the pure intelligence he has grasped the real nature of good - he arrives at the very end of the intellectual world.

The Republic of Plato, Translated Into English, with an Introduction, Analysis, and Notes. By J. Ll. Davies and D. J. Vaughan (ed. 1852)