 That the discussion does not end here but occupies six more books, is due most of all to several loose ends that need to be tied up. Apart from the fact that reason and order are to reign supreme, little has been said about the citizens’ way of life. This gap will be filled, at least in part, by the description of the communal life without private property and family in Book V. More importantly, nothing has been said about the rulers and their particular kind of knowledge. This is a crucial point because, as the definitions of the three ‘inferior’ virtues show, their quality is contingent on the rulers’ wisdom. Socrates addresses this problem with the provocative thesis (473c–d): “Until philosophers rule as kings or those who are now called kings and leaders genuinely and adequately philosophize ... cities will have no rest from evils, nor will the human race.” This thesis starts the discussion of the philosophers’ knowledge, and of their upbringing and education, which will continue through Books VI and VII. Because they also introduce the special objects of the philosophers’ knowledge, these books provide the metaphysical underpinning of the entire conception of the good state and of the good soul. For the ‘Form of the Good’ turns out to be the ultimate source of all being and knowledge. A short summary of the upshot of the educational program must suffice here. The future philosophers, both women and men, are selected from the group of guardians whose general cultural training they share. If they combine moral firmness with quickness of mind, they are subject to a rigorous curriculum of higher learning that will prepare them for the ascent from the world of the senses to the world of intelligence and truth, an ascent whose stages are summed up in the similes of the Sun, the Line, and the Cave (508a–518b). To achieve this ascent, the students have to undergo, first, a preparatory schooling of ten years’ duration in the ‘liberal arts’: arithmetic, geometry, astronomy, and theoretical harmonics (518c–531c). Afterwards they are admitted to the training in the master-science of ‘dialectic’, a science of which little more is said beyond the indication that it enables its possessor to deal in a systematic way with the objects of real knowledge – the Forms in general, – and with the Form of the Good, – the principle of the goodness of all else, – in particular (531c–535a). This study is to last for another five years. Successful candidates are then sent back into the Cave as administrators of ordinary political life for about 15 years. At the age of fifty the rulers are granted the pursuit of philosophy, an activity that is interrupted by periods of service as overseers of the order of the state. This completes, in a nutshell, the description of the philosopher-kings’ and -queens’ education and activities (539d–541b).