They have been intoxicated with great ideas, such as liberty, or equality, or the greatest happiness of the greatest number, or the brotherhood of humanity, and they no longer care to consider how these ideas must be limited in practice or harmonized with the conditions of human life.

They are full of light, but the light to them has become only a sort of luminous mist or blindness.

Almost every one has known some enthusiastic half-educated person, who sees everything at false distances, and in erroneous proportions.
With this disorder of eyesight may be contrasted another--of those who see not far into the distance, but what is near only; who have been engaged all their lives in a trade or a profession; who are limited to a set or sect of their own.

Men of this kind have no universal except their own interests or the interests of their class, no principle but the opinion of persons like themselves, no knowledge of affairs beyond what they pick up in the streets or at their club.

Suppose them to be sent into a larger world, to undertake some higher calling, from being tradesmen to turn generals or politicians, from being schoolmasters to become philosophers:--or imagine them on a sudden to receive an inward light which reveals to them for the first time in their lives a higher idea of God and the existence of a spiritual world, by this sudden conversion or change is not their daily life likely to be upset; and on the other hand will not many of their old prejudices and narrownesses still adhere to them long after they have begun to take a more comprehensive view of human things?
From familiar examples like these we may learn what Plato meant by the eyesight which is liable to two kinds of disorders.
Nor have we any difficulty in drawing a parallel between the young Athenian in the fifth century before Christ who became unsettled by new ideas, and the student of a modern University who has been the subject of a similar 'aufklarung.' We too observe that when young men begin to criticise customary beliefs, or to analyse the constitution of human nature, they are apt to lose hold of solid principle (Greek).