Part 4: When the students are 30, a further selection is made. (Socrates does not specify what happens to the students who are not selected at this stage.) The students who are selected will study Dialectic for about five years, and care must be taken to show the students that the study of Dialectic is a serious enterprise; it is not a game of wits undertaken for personal grandeur.
Part 5: When they are 35, having now become trained philosophers, the students will receive the practical experience necessary for them to accept their role as leaders of the state. They will take positions in the military and politics and begin teaching their fellow citizens to "see the light," so to speak. This period of service will last 15 years.
Part 6: At the age of 50, the philosopher-rulers will be fully matured. They will now spend the rest of their lives in philosophical contemplation and in ruling and governing the Ideal State. Now that they know Goodness, they will best be prepared to serve the good of the state.
