Plato gives a very detailed dialogue in the Republic about what is justice and why it is a better choice than injustice. In order to better understand the text, I would like to summarize it from my on account and give my analysis on it in different sections.
Socrates refutes three main arguments about justice from Caphalus, Polemarchus, and Thraymachus. In order to discover what true justice is, Socrates engages in some interesting dialect. Firstly, Socrates wants to define the ideal city and what parts and people are integral to it. The purpose is to try to understand justice on a larger scale so that we can clearly define the proponents of it that will easily translate to a smaller scale like the human soul. He compares it to when a person checks his eye sight by reading off the largest letters then gradually reading increasingly smaller letters. In biology we used to compare the dynamics of a city to the anatomy of the human body. The supermarkets and restaurants are like the stomach, the streets and transportation resemble the veins and arteries and the government building is like the brain.
If we can understand how justice works within the city, then we can apply it to the human soul and how it functions. Socrates explains that the city should consist of three different classes; the producers (farmers and craftsman), the auxiliaries (warriors), and the guardians (rulers). In order for justice to prevail, all three of these classes must do their own part in society; "Every other citizen, too, must be assigned to what naturally suits him, with one person assigned to one job so that practicing his own pursuit, each of them will become not many but one, and the entire city thereby naturally grow to be one, not many." Justice is a form of order and harmony. Therefore having one united group with all individuals doing their own work for the happiness of all is just.
The three different classes producers, auxiliary, and guardians parallel to the three parts of the soul respectively; appetitive, spirited, and rational. The appetitive element feels passion, hunger, and thirst stirred by other appetites like money especially. The spirited part desires honor and is responsible for our feelings of anger. The rational section seeks truth and controls the other elements. Just as the guardians rule, the warriors support the rulers, and the producers obey them, the rational, spirited, and appetitive elements follow suit. When all three of these elements are fulfilling their purpose and working in harmony, then the city and the soul have achieved justice.
Plato emphasizes that only education can allow people and cities to achieve justice. That is because by understanding the elements and how they function is the only way to know how to control them. A very loose analogy would be like when I am in the weight room and the coaches explain to me exactly what this exercise is doing, what muscles it is engaging, and how it will enhance my strength which allows me to better execute the exercise overall. My comprehension of how the body works, how it gets stronger, and what foods to fuel it help me become a better athlete. I am able to control my body through knowledge of it. Plato would explain that the same knowledge about the soul better enhances its own performance and your authority over it. By education, moderate men will discover order for themselves, produce good natures, and be better than the previous generation.
An extensive system of the type of education children should receive is drawn out by Plato, but he clearly states that the aim of education is not to put knowledge into the soul, but to put the right desires into it. He paints a picture of the journey to true intellect using three different analogies. The first is of the sun and how it gives light to things and makes things visible to the eye. The soul can be thought of the same way. When it focuses on something that is illuminated by the truth and is revealed to be what it really is then the soul is able to understand it. However, when the soul looks at something dim and obscure, it changes its beliefs and is lost of understanding. Socrates explains, "What gives truth to the things known and the power to the knower is the form of the good. And as the cause of knowledge and truth, you must think of it as an object of knowledge…Light and sight are right thought to be sun-like, but wrongly thought it be sun. So, here it is right to think of knowledge and truth as goodlike, but wrong to think that either of them is the good-for the status of the good is yet more honorable." Also, the sun not only gives us power to see but nourishment like "objects of knowledge owe their being known to the good, but their existence and being are also do to it; although the good is not being, but something yet beyond being, superior to it in rank and power."
This can be contrasted to Plato's other visual aid of the division of the line. The world is divided into two realms, the visible, which we grasp with our senses, and the intelligible, which we grasp with our mind. WIthin these two sections there are two subsections. The visible consists of one part shadows and reflections (illusion) and the other real objects we see (beliefs). The intelligible subsections are much more complex and easier to explain in mathematical terms. In geometry when are doing a proof to a theorem, there are certain facts that are undisputed like three sides to a triangle. Those claims can be put under mathematical reasoning. The higher level subsection is called philosophical reasoning because you not only use the evidence found in the mathematical reasoning to conclude things, but actually understand the conclusion, the bigger picture, or the forms. Understanding justice and the examples of it is different than grasping the source of justice, which is the good.
Plato also explains his famous allegory of the cave in the Republic. He describes a group of people be chained and facing a blank wall. Shadows move across the wall and the prisoners take that as reality. Then when the prisoner is able to break away from their enslavement, they see the shadows being created by figures in front of a fire. At first they are blinded by the brightness of the fire and retreat their eyes to the shadows of the wall. The prisoner will not want to enter the sunlight above the cave because he is afraid of its pain. When he is dragged up to the top, his eyes burn from the light. When they slowly acclimatize, he can only see the shadows of the objects above at first. Then he is finally able to look up at the object and later the sun itself. He realizes that the sun is the source of everything; the seasons, years, and sight.
These analogies explain the painstaking task of discovering true intellect and understanding the form of the good. Without this knowledge, justice will never be achieved. Plato understood that this was not achievable by all people. That is why it is important for the rulers to be philosophers that seek wisdom and know truth. The warriors and producers will do their parts in society because they have laws to reinforce their education that allows them to find truth for themselves to the best they can. The city as a whole will function properly with all parts aligned, while each individual soul is at peace.
