There are two basic ways in which the phenomenon of learning is explicated in the Platonic dialogues: First, by means of an analogy with vision, and second, by arguing that the acquisition of knowledge is really anamnesis (recollection). The analogy with vision is the more common of the two and occurs throughout the dialogues. The passage in the Republic comparing the sun and the good (508c-509b) is the best known instance of this approach to the clarification of learning. The basic point of this explication is that the mind, like the eye, in order to discover truth must be turned in the right direction and be trained to apprehend and distinguish the characters of the objects it beholds. In this context, the acquisition of knowledge is clearly a discovery of that which was not previously known, just as the man who escapes from the cave sees what he had not previously seen (Republic, 514a-516c), and at the end of the ascent of the heavenly ladder one “begins to see” what he has not seen before (Symposium, 211b 8).