We have already mentioned Solon's contention against literature--that poets are liars, or that poets lie too much. Xenophanes, Parmenides and Heraclitus are reported by Plato to have attacked Homeric theories of inspiration. They also oppose the notion of the poet being a wise man or a prophet. They probably believed the poet to be but the spokesman of dóxa or vulgar opinion: only philosophers can see through dóxa and understand reality.
Democritus, on the other hand, defends the theory of inspiration: he believes that the poet is a divine madman. We shall find this notion again in Plato and in many romantic theories of poetry.
Pythagoras, or rather the Pythagoreans, for Pythagoras himself is a shadowy figure, developed a whole theory of reality which foreshadows Platonism. Number is thought to be the basis of the universe. All things could in theory be reduced to numerical relationships, that is, the structure of reality can be given a mathematical formulation. The Pythagoreans made some substantial advances in mathematics, and also in the theory of music. They see music as one clear instance of the numerical structure of reality, and the mathematical study of music can be traced up to them. Pythagorism developed into a kind of aristocratic religion, a cult of small self-enclosed groups pervaded with secrecy and strange rituals. Music had an important part in that religion. They believed it had positive effects on the soul, something between therapeutic and ethical. Just as the world is number, harmony is a mímesis of that numerical structure. We could also say that the universe is harmony. The human soul, too, is a kind of harmony, and music can restore it whenever it is out of tune with the whole. The notion of mimesis is an important one, as is that of the psychological effects of music. We will find similar ideas later in Plato, Aristotle and Plotinus.
The sophists (5th century BC) seem to be responsible for the origins of systematic work on poetics and rhetoric. According to Stephen Halliwell, "the idea of a specialised discursive theory of poetic standards, or of communicable techniques of judgement, was a new phenomenon in the fifth century, and in this general respect, Aristotle was heir to the sophists." Many sophistic treatises on poetry and rhetoric must have been known to Aristotle, thought they have since been lost. There remain only scattered fragments and references to their work. Sophistic teachings were prescriptive: their aim was to teach how to speak and write successfully. Some of their work on linguistics is also relevant to literature.
The sophist Gorgias answers to those philosophers who speak of poets as a kind of liars. He says that poetry is a form of deception all right, but that the deceived is wiser than the undeceived. This is the first instance of a theoretical basis for a theory of fiction which goes beyond the question of the sincerity of the poet or the historical truth of poetry. In another fragment, Gorgias defines poetry as "discourse subject to rhythmical measure." It is discourse, language, but a special kind of language. The sophists point out that prose and poetry are not so far apart as they seem to be. They find that prose language, too, can be embellished with figures. They speak of two kinds of embellishment: gnomology , or embellishment throught the use of maxims, and eikonology, or embellishment of discourse through the use of images. There are several kinds of images, and later students of rhetoric will inherit and develop the achievements of the sophists in studying the figures of speech and thought.
Protagoras, best known for his saying that man is the measure of everything, classifies for the first time what we might call the functions of language, or, from another perspective, the kinds of speech acts. He calls them "grounds of discourses," and says that there are four: request, question, answer, order. He even applies them in a somewhat fastidious way to literature when he criticises Homer, after all a mere mortal, for giving orders to the muse in the invocation of the Iliad. Later sophists will propose different classifications of the kinds of discourses, distinguishing up to seven types of discourse. We notice that poetry, literature or fiction are not considered to be a different type of discourse in these classifications, and they are considered to be analysable with the same tools as the other uses of language.