Along with written speech, the Greeks commenced studying grammatical and philosophical issues. A philosophical discussion about the nature and origins of language can be found as early as the works of Plato. A subject of concern was whether language was man-made, a social artifact, or supernatural in origin. Plato in his "Cratylus" presents the naturalistic view, that word meanings emerge from a natural process, independent of the language user. His arguments are partly based on examples of compounding, where the meaning of the whole is usually related to the constituents, although by the end he admits a small role for convention. The sophists and Socrates introduced dialectics as a new text genre. The Platonic dialogs contain definitions of the meters of the poems and tragedy, the form and the structure of those texts (see the "Republic" and "Phaidros", "Ion", etc.).