There is no such thing as absolute truth. Truth is only a relative term. When a man speaks of the truth he means those doctrines which he himself embraces. Every man believes that the views that he entertains are true, otherwise he would not hold them. Many people have in the past died for the "truth," when we know that they upheld falsehood.
A writer who is liberally inclined will hold liberal ideas to be the truth; a conservative regards only conservative views as true. An author who embraces ideas from both the conventional and radical spheres, considers only those books as true whose authors do the same thing.
In a sane essay on De Vigny, Mill makes a remarkable distinction between the conservative and radical poet, concluding that the greatest poet will always partake of the nature of both, mentioning as example Balzac and De Vigny. Had he written on the subject a half-century later he might have named Ibsen, whose _Brond_ and _Wild Duck_ are good conservative poems. Mill, who was no disciple of art for art's sake, said that the radical poet will paint passionate love, "will show it at war with the forms and customs of society, nay even with its laws and religion, if the laws and tenets which regulate that branch of human relations are among those which have begun to be murmured against." "To him, whatever exists will appear from that alone fit to be represented: to probe the wounds of society and humanity is part of his business, and he will neither shrink from exhibiting what is in nature, because it is morally culpable, nor because it is physically revolting." Here Mill anticipates Zola, Ibsen and Freud. No wonder that so radical a critic as Brandes was attracted to him. It is a pity he did not continue literary criticism.
It is probably vain to try to define different types of poetic or literary excellence, but we may state some of these. Formerly a first-class poet was one who successfully imitated a model and followed certain rules. Or he was one who successfully voiced the current accepted views of the age. It is these reasons that still make many people consider Dante and Milton among the first-class poets. Again there is a tendency to regard as poets of the first class those who perfected their art technically. Hence Æschylus and Sophocles are ranked among the greatest poets. Sometimes he is regarded among the greatest poets because he is among the earliest, like Homer. The position of poets like Shakespeare, Molière, Cervantes and Goethe as first-class world poets and writers, cannot be contested, because they are so universal.