Editor’s note: Sixth in a series.
The previous essay concluded on a new note: the idea of a moral universe, and I have returned to Plato as my guide.
Plato did not suppose that a moral universe is a world where everyone may expect rewards for their good deeds and punishments for their evil ones, now or hereafter. Rather, he imagined something higher and nobler; a universe in which Goodness itself is the beginning and end of everything.
It is this sort of world that he describes in “The Republic.”
“The Republic” is a dialogue, it presents a conversation that purportedly took place in Athens 2500 years ago between Socrates and three young men, two of them were Plato’s older brothers, Glaucon and Adeimantus. The topic was justice.
Socrates narrates. He tells how the young men challenged him to prove that it is better to be just than unjust, and that only those who live justly will be happy and fulfilled. They claimed that most people paid lip service to justice, but few tried to practice it or even bothered to learn the meaning of the word; those who tried to live justly were regarded as fools or pretenders, more likely the latter.
But for Plato’s brothers, the question whether a just life can be happy and fulfilling was profoundly existential, for they desired to be just and longed to exist in a just world.           
Justice is a virtue, one of the four cardinal virtues or moral excellences: the other three are courage, temperance and wisdom. Anticipating Hobbes, Plato supposed that civil society is comparable to a living animal, and that it can be happy or unhappy, depending on the character of its corporate life. Justice is the primary virtue of a civil society or state.
Socrates proposes to discover the nature of justice and its true value by observing how it operates in a hypothetical city or city-state, and following that, whether the city is happy. It is a larger object, and the details are easier to see.
So, Socrates undertakes to describe a just city. He supposes that societies are created because humans are not self-sufficient animals: there is a diversity of talents and capabilities among us, and we depend on others to provide for our needs, and for the benefits that make life not only durable but pleasant and enjoyable.
The prospect for happiness, Socrates continues, depends on everyone finding their niche in society; only then, when all have the means to meet their needs, to practice their crafts and secure those added benefits that make life worth living, will their life together in society be happy.
But they must also provide for their safety.
Hence, every civil society requires a class of persons, men and women, who are able not only to protect it and but also to ensure that it is well ordered, to govern it. They are its guardians. “The Republic” is mostly about them, their physical and moral qualities, their training and education, their form of life and their prospects for happiness.
It is agreed that the guardians of a city must be strong, brave, temperate and wise, and, above all, just. But in order to be just, they must be wise, for a city cannot become just unless it is founded on truth.
Therefore, Guardians must be lovers of truth, for no one can properly administer justice who does not know the truth. 
This leads to the observation that the expression “lover of truth,” resembles the expression “lover of wisdom,” and inasmuch as wisdom and truth seem to be virtually the same, we can treat them as one and interchangeable expressions. That leads Socrates to conclude, with some embarrassment, that only philosophers are fit to rule, which is the origin of the now hackneyed expression “philosopher-king.”
Guardians must be endowed with a boundless curiosity, a desire to know all things, which is not being acquainted with how they look or seem, but how or what they really are. It is such curiosity that has even found a place in a child’s nursery rhyme:
Twinkle, twinkle, little star,
How I wonder what you are!
Up above the world so high,
Like a diamond in the sky.
Socrates, or maybe his prize pupil Plato, is the first to distinguish between the fact that a thing exists and what it is, which has come to be known as its essence in contrast to its mere existence.
Aristotle, Plato’s pupil, developed this further into a new science, now commonly called “metaphysics,” which is the study of essences, the study of that which is as something that is, as being a certain sort of thing. The proper expression of an essence is a definition.
But among the things that are in Plato’s moral universe, there are not only bodies, animate or inanimate, but other things, which we commonly take as mere abstractions, objects of thought, but when raised to a higher plane become Ideals, such as the Good itself, and the True, Beauty and Justice.
And he came to believe that these intangible objects of the mind are more real than the tangible things of our everyday life. These high abstractions are not merely ideas to be contemplated, and perhaps imitated, they are the causes of everything that is.
Thus, Plato’s moral universe is one that not only contemplated the top; it is from the top that all things originate.
I should say more, but I have run out of space.  I have more to say, including why Plato believed that only a moral universe is a happy one.
To be continued. 
Postscript: A problem that Plato acknowledged, but did not pursue, is the origin of evil. He was perplexed by it, for if a moral universe is one in which the Good itself is the beginning and end of everything, then, since the Good, like Justice, can do no harm, it cannot be the cause of evil. In the Fourth Gospel, Jesus describes the devil, the source of absolute evil, as “a liar and the father of lies,” which is suggestive. It also fits the current state of things in Washington.