It is important to realize, when reading the allegory of the cave and of the line, that Plato means to depict not only four ways of thinking, but four ways of life. To use an example, imagine that a person in each of these stages were asked to say what courage is. The understanding of courage would differ widely from stage to stage. Working with a possible interpretation of the imagination stage, an individual’s notion of courage in this stage would appeal to images from culture. Such an individual might try to explain courage by saying something like, “Luke Skywalker seems really courageous, so that’s courage.
An individual possessed of beliefs would also appeal to a particular example, but the example picked would be drawn from real life. There might be mention of the Marines or New York City firemen. Someone at the stage of thought, in contrast, will try to give a definition of courage. Perhaps they will give the definition offered by Socrates in Book IV: courage as the knowledge of what is to be feared and what is not to be feared. What separates the person speaking from thought from the person possessed of understanding is that the person speaking from thought cannot inform his views with knowledge of the Form of the Good.
They are working with unproven hypotheses rather than the true first principle. Even if their definition is correct, it is left open to attack and objection because their grasp of the relevant concepts stops at a certain point. Speaking from understanding, someone giving a definition comprehends all the terms in the definition and can defend each one of them based on the first principle, the Form of the Good. Because the Form of the Good illuminates all understanding once it is grasped, knowledge is holistic.
You need to understand everything to understand anything, and once you understanding anything you can proceed to an understanding of everything. All the forms are connected, and are comprehended together in the following way: you work your way up to the Form of the Good through thought until you grasp the Form of Good. Then, everything is illuminated. Since the stages in the cave are stages of life, it seems fair to say that Plato thought that we must all proceed through the lower stages in order to reach the higher stages.
Everyone begins at the cognitive level of imagination. We each begin our lives deep within the cave, with our head and legs bound, and education is the struggle to move as far out of the cave as possible. Not everyone can make it all the way out, which is why some people are producers, some warriors, and some philosopher-kings. Given that the philosopher-kings have made it out of the cave, it might seem unfair that they are then forced back in. This is the worry that Socrates’s friends raise at the end of this section. Socrates has three lines of response to this concern.
First, he reminds us again that our goal is not to make any one group especially happy, but rather to make the city as a whole as happy as possible. Second, he points out that the philosopher-kings are only able to enjoy the freedom above ground that they do because they were enabled by the education the city afforded them. They were molded to be philosopher-kings so that they could return to the cave and rule. They owe the city this form of gratitude and service. Finally, he adds that the philosophers will actually want to rule—in a backhanded way—because they will know that the city would be less just if they refrained from rule.
Since they love the Forms, they will want to imitate the Forms by producing order and harmony in the city. They would be loathe to do anything that would subject the city to disorder and disharmony. Socrates ends by remarking that the reluctance of the philosopher to rule is one of his best qualifications for ruling. The only good ruler rules out of a sense of duty and obligation, rather than out of a desire for power and personal gain. The philosopher is the only type of person who could ever be in this position, because only he has subordinated lower drives toward honor and wealth to reason and the desire for truth.