[111] Plato, Republic, iv. pp. 442 C, 443 B.
A man as well as a city is just, when each of his three sorts or varieties of mind confines itself to its own legitimate function: when Reason reigns over and controuls the other two, and when Energy seconds Reason in controuling Appetite. Such a man will not commit fraud, theft, treachery, perjury, or any like proceedings.[112] On the contrary, injustice exists when the parts are in conflict with each other: when either of them encroaches on the function of the other: or when those parts which ought to be subordinate rise in insurrection against that which ought to be superior.
[112] Plato, Republic, iv. pp. 442-443.
Justice and Injustice in the mind — what health and disease are in the body.
Justice is in the mind what health is in the body, when the parts are so arranged as to controul and be controuled pursuant to the dictates of nature. Injustice is in the mind what disease is in the body, when the parts are so arranged as to controul and be controuled contrary to the dictates of nature. Virtue is thus the health, beauty, good condition of the mind: Vice is the disease, ugliness, weakness, of the mind.[113]
[113] Plato, Republic, iv. p. 444 B-C.
Original question now resumed — Does Justice make a man happy, and Injustice make him miserable, apart from all consequences? Answer — Yes.
Having thus ascertained the nature of justice and injustice, we are now in a condition (continues Sokrates) to reply to the question proposed for investigation — Is it profitable to a man to be just and to do justice per se, even though he be not known as just either by Gods or men, and may thus be debarred from the consequences which would ensue if he were known? Or is it profitable to him to be unjust, if he can contrive to escape detection and punishment? We are enabled to answer the first question in the affirmative, and the second question in the negative. As health is the greatest good, and sickness the greatest evil, of body: so Justice is the greatest good, and injustice the greatest evil, of mind. No measure of luxury, wealth, or power, could render life tolerable, if we lost our bodily health: no amount of prosperity could make life tolerable, without mental health or justice. As bodily health is good per se, and sickness evil per se, even apart from its consequences: so justice also is good in itself, and injustice evil in itself, apart from its consequences.[114]
[114] Plato, Republic, iv. p. 445 A.
Glaukon requires farther explanation about the condition of the Guardians, in regard to sexual and family ties.