These questions deal with Plato's Euthyphro and books 4, 6, and 7 of the Republic.God and Ethics
These materials are copyrighted (c) 1998 by Harry J. Gensler; but they may be distributed freely.
Plato's Euthyphro focuses on the meaning of "good" (or "holy") and how this connects with God's will (or "what the gods love"). The dialogue asks: "Is a thing good because God desires it -- or does God desire a thing because it is good?"Individuals and Ethics
Plato thinks the second alternative is the right one. God's desire doesn't MAKE a thing good or bad. Rather, God first KNOWS that a thing is good, and THEN desires that thing.
Plato thus rejects the divine command theory (which says that God's will MAKES things good or bad). Plato seems to hold intuitionism (which says that things can be inherently good or bad).
In Plato's Republic, the four cardinal virtues are wisdom, temperance, courage and justice. These reflect the nature of the soul.Society and Ethics
The soul has three parts. Our reason thinks; when it does this well, it has wisdom. Our appetite desires; when it does this well, it has temperance (self-control, soberness). Our "high spirit" shows emotions (fear, anger, respect, etc.); when it does this well, it has courage.
Justice consists of the proper interplay of the three parts of the soul. In the just person, reason controls the "high spirit" -- and both control the appetite.
In Plato's Republic, society mirrors the individual soul. And the virtues of society mirror the virtues of the individual soul.The GOOD
Society has three groups. The aristocrats are the educated; they should be wise. The workers (merchants, commoners) do the work; they should be temperate (have self-control). The soldiers (guardians) protect the city; they should be courageous (brave).
Justice in society is the proper conformity of the three groups to their social roles. Each group has its own place, according to its natural abilities. The aristocrats are to rule wisely, and the other groups are to obey and to do their own tasks. This will promote the happiness of the city and of its members.
The GOOD is not an object of sense. It isn't pleasure, since there are bad pleasures. The GOOD is an object of reason.
The highest reality and knowledge isn't that of the visible world. Rather, the highest reality and knowledge is of the intelligible world (the world of reason, of ideas, of the forms). The GOOD is the ultimate source of the existence and knowability of this higher world.
We know the GOOD by the rational grasp of first principles (like the axioms of geometry). We grasp these by our recollection from a previous existence. These first principles are the source of the wisdom that the "philosopher king" of the Republic requires. But this wisdom is beyond our ordinary ways of thinking, as the allegory of the cave shows.