This extract is from Plato’s Republic, Book V.
Glaucon said: If curiosity makes a philosopher, you will find many a strange being will have a title to the name. All the lovers of sights have a delight in learning, and must therefore be included. Musical amateurs too, are a folk strangely out of place among philosophers, for they are the last persons in the world who would come to anything like a philosophical discussion if they could help; while they run about at the Dionysiac festivals as if they had let out their ears for the season to hear every chorus, and miss no performance either in town or country. Now are we to maintain that all these and any who have similar tastes, as well as the professors of quite minor arts, are philosophers?
Certainly not, I replied; they are only an imitation.
He said: Who then are the true philosophers?
Those, I said, who are lovers of the vision of truth.
That is also good, he said; but I should like to know what you mean?
To another, I replied, I might have a difficulty in explaining; but I am sure that you will admit a proposition which I am about to make.
What is the proposition?
That since beauty is the opposite of ugliness, they are two?
And inasmuch as they are two. each of them is one?
And of just and unjust, good and evil, and of every other form, the same remark holds: taken singly, each of them is one; but from the various combinations of them with actions and bodies and with one another, they are seen in all sorts of lights and appear many?
And this is the distinction which I draw between the sight-loving, art-loving, practical class which you have mentioned, and those of whom I am speaking, and who are alone worthy of the name of philosophers.
The Dialogues of Plato, translated by Benjamin Jowett, Volume Four, The Republic, edited by M Hare & DA Russell, Sphere Books Ltd., 1970, Book V (475d-476b), p.255.