Chapter 3 of Book 5

Knowledge Versus Opinion

by Socrates Icon
Socrates Then let us enact this law that our guardians are neither to devastate the lands of Hellenes nor to burn their houses.

Yes, these and all our previous enactments, are very good. But how can it be done?

Your citizens will be the bravest of warriors. They will all know one another and will call the other father, brother, son. If the women will join their armies then they will be absolutely invincible. There are many domestic advantages as well. But how to we bring about such a State?


We ended up here through our search for justice and injustice. In order to have an ideal, we enquired into:

  • the nature of absolute justice,
  • the character of the perfectly just,
  • the nature of injustice,
  • the character of the perfectly unjust.

We looked at these so that we could compare our own happiness and unhappiness to the standard, without imagining how that standard could exist in reality. A painter would not be any worse if he painted an ideal man, but was unable to show how such a man could exist.

We were creating an ideal of a perfect State. Our theory is not worse because we are unable to prove the possibility of such an ideal city. Are “ideals” ever fully realized in language?

Glaucon The word “ideal” expresses not an actual fact.

Whatever a man may think always naturally falls short of the truth. You must not insist the actual State will coincide with the ideal in every respect. If we are only able to discover how a city may be governed as ideally as possible, then we have achieved our goal. I will next show:

  • what causes the present maladministration in States, and
  • what is the smallest change that will enable a State to pass into the truer form.

The changes should be as few and slight as possible. There might be a reform of the State if only one change were made. This is not small or easy, but it is still possible. The greatest change is like the greatest of the waves. It can drown me in laughter and dishonour. The human race will always have evils unless:

  • philosophers are kings,
  • the kings have the spirit and power of philosophy,
  • political greatness and wisdom meet in one, or
  • those of commoner natures are compelled to stand aside.

Our State will have a possibility of life if those conditions are met.

Philosophers as Rulers of the Ideal State


Philosophers are to rule in the State. Not all people are meant to be philosopher-leaders. But those who are should study philosophy and be leaders in the State.

A lover should show his love to the whole. Young people raise a pang or emotion in a lover’s breast. Sensual people praise a charming face and say that:

  • a hook-nose is a royal look
  • a snub nose is a fair look
  • a regular look is to have neither a hook-nose or a snub nose

Ambitious men are willing to command a file if they cannot command an army. If they cannot be honoured by important persons, they are glad to be honoured by lesser people. They must have some kind of honour.

A person who desires any class of goods, desire the whole class. The philosopher is a lover of the whole of wisdom. A person who is curious to learn and is never satisfied may be justly called a philosopher.

Glaucon If curiosity makes a philosopher, then many are philosophers.
Socrates All the lovers of sights have a delight in learning, and must therefore be included. This includes musical amateurs who are the last persons in the world who would come to a philosophical discussion. Are these all philosophers?
Glaucon Certainly not, they are only an imitation.

The true philosophers are the lovers of the vision of truth. Beauty is the opposite of ugliness, but is one with it. The same is true for the just and unjust, good and evil, and of every other class.

But they have various combinations in actions and things and appear to be many. This is my distinction between the sight-loving, art-loving, practical class and those of truth-loving class who are alone worthy to be called philosophers.

Glaucon How do you distinguish them?

The lovers of sounds and sights are fond of fine tones, colours, forms, and all the artificial products made out of them. But their mind cannot see nor love absolute beauty. Few can see it. He who has a sense of beautiful things has no sense of absolute beauty.

The dreamer likens dissimilar things and puts a copy in the place of the real object.But the person who recognises absolute beauty and is able to distinguish the idea from its objects. He does not put the objects in the place of the idea nor the idea in the place of the objects. He is awake and not a dreamer.

The dreamer has opinion only. The awake person has knowledge. If the dreamer disputes us, we shall we assure him that he is welcome to any knowledge which he may have. We ask him= Does he who has knowledge know something or nothing?

Glaucon He knows something.

Knowledge is a Sense or Faculty


An absolute being can be absolutely known, but an utterly non-existent being is utterly unknown. If there is anything that exists and not exists, then it will be in-between pure being and the absolute negation of being.

Knowledge corresponds to being*. Ignorance corresponds to not-being. The intermediate between being and not-being has a corresponding intermediate between ignorance and knowledge.

The existence of opinion is the same with the existence of knowledge or some other faculty. Then opinion and knowledge have to do with different kinds of matter corresponding to this difference of faculties. Knowledge is relative to being and knows being.

*Superphysics Note: Being here is the same as Existence. Hume defines truth as the equivalence between perception and existence. Therefore, knowledge is the match between ideas and perceptions, with the ideas being ‘facts’. Opinion is the possible equivalence of ideas and perceptions. Truth, knowlege, and opinion are therefore dependent on the faculty of perception, which is why Plato assigns knowledge and opnion as faculties. Knowledge and opinion differ between humans because humans have different levels of perception, just as some humans are color-blind, short-sighted, deaf, ignorant, etc.


For example, I call sight and hearing as faculties. If I do not see something then the distinctions of figure, colour, etc. do not apply to them. In speaking of a faculty, I think only of its scope and its result.

The same faculty has the same scope and the same result. Another faculty has a different sphere and result.


Knowledge is the mightiest of all faculties. Opinion is also a faculty. Opinion is the faculty that lets us form an opinion. Knowledge is not the same as opinion because no one will mistake an infallible thing with an erroneous thing.

Knowledge and opinion have distinct powers and distinct scopes or subject-matters.

  • Being is the subject-matter of knowledge. To have knowledge is to know the nature of being.
  • Opinion is the subject-matter of opinion. To have an opinion is to have a limited or biased knowledge.
Glaucon The difference in faculty implies a difference in the subject-matter. Opinion and knowledge are distinct faculties which have different subject-matters.

The Nature of Opinion

Socrates What is the subject-matter of opinion? It cannot be being, yet it cannot be not-being or nothing.
Glaucon Yes, it is impossible to have an opinion on nothing.

Therefore, the subject-matter of opinion is the in-between of knowledge and ignorance.

This ‘in-between’ cannot be rightly called as “pure” and “simple”. Instead, we can call this “the subject of opinion.”

The double of one thing is a double to the perspective of that thing. But to the perspective of an outsider, it is the half of that thing. The same is true for big and small, heavy and light, beautiful and ugly. The multiple variations of beautiful and ugly are created by the different opinions of the multitude from their various perspectives.

Glaucon You cannot fix this duality or its variations in your mind, either as being or not-being, both, or neither. Then what will you do with them?

This duality is the intermediate flux which is caught and detained by the intermediate faculty of opinion.

Those who see the absolute, eternal, and immutable have knowledge and not opinion only. These love the subjects of knowledge.

But those who have no knowledge and only opinion are those who:

  • see only relative beauties but not the absolute beauty
  • follow any guide who points the way those relative beauties
  • see the relative justice, but not absolute justice
  • love the subjects of opinion
  • listen to sweet sounds and gaze on fair colours

They would not tolerate the existence of absolute beauty. We can call them lovers of opinion rather than lovers of wisdom.

They might be angry at us for this.

Glaucon I shall tell them not to be angry. No man should be angry at what is true.
Socrates Those who love the truth in each thing are to be called “lovers of wisdom” and not “lovers of opinion”.

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