The distinction that underpins the three broad divisions of genre have their origins in the rigid formalities and hierarchies of classical thought. Book 3 of Plato's Republic (c. 380 B.C.E.) is preoccupied with the effective censoring of writing deemed inappropriate to the dignity of the projected Republic and its guardians. Though this activity finds its parallel in Aristotle's later consideration of "decorum," or the proper relationship of style to subject matter, Plato's dialogue is most influential in its systematization of genre, albeit in a vision premised upon the perception of narrative voice through direct speech, rather than a more protracted encounter with technique in itself, as the primary item of definition. Plato's division, contained for the most part within what are traditionally numbered paragraphs 392–396 of Book 3, contends that "any poem or story deals with things past, present or future" by way of "either simple narrative, or representation, or a mixture of both" (p. 131). The division here is based upon the relative positions of the poet allegedly speaking as himself ("narrative") and the imitative function whereby the speech or manner of another person is imitated in an act of "representation." Using Homer's Iliad as an example, the dialogue further develops the presence of a hybrid form in which passages of narration alternate with those of representation, the poet speaking first "in his own person" and then "in the person of Chryses" (p. 131). Notably, the later genre distinction between "poetry [and] drama" is ignored in this early classification, the "styles" of narration being the only distinction permitted to those engaged in the act of creation.
The most influential classical formulation of discrete and persistent genre criteria based upon a perceived difference in media as much as on the condition of narrative voice and subject matter is in Aristotle's undated treatise On the Art of Poetry (also known as The Poetics), though it is apparent that the work may have had limited currency from antiquity until its rediscovery during the Renaissance. The treatise is committed to a hierarchical differentiation of poetry, Aristotle's introductory history of poetic writing acknowledging an early division of art into "two channels": a "serious-minded" tradition preoccupied with "noble actions and the doings of noble persons" (p. 35) and a more invective, trivial form that charted the dealings of the "meaner sort of people" (p. 36). Three different methods of distinguishing the essential nature of a work are outlined in the Poetics, these being the medium (effectively the verse or rhythmic form) through which a work may imitate reality; the "object of imitation" (how a character is represented or exaggerated—in Aristotle's contention, specifically in moral terms); and finally (and in continuation of the Platonic model), the "manner of imitation" or difference between representation and narration (pp. 32–34).
The hierarchical model exercises itself within the Poetics through the distinction between the qualities of tragedy, comedy, and epic. Comedy, it is suggested, is a "low" form, in that it is a projection of the ridiculous or of that which is painful to perceive, though this is undertaken in such a manner as not to cause pain to the audience. One would add to this the assumption that such a form would be unlikely to provoke deep thought or self-reflection, though developments in the satirical tradition of Roman literature might well achieve this. In Aristotle's understanding, Greek epic and tragedy, in contrast to comedy, do provoke introspection, both laying claim to be "a reflection, in dignified verse, of serious actions" (p. 38)—though Aristotle eventually concludes the tragic to be the more effective and thus the most prestigious of the two.
Epic differs from tragedy also through formal conventions. According to Aristotle, epic, alone, conventionally "keeps to a single metre and is in narrative form" (p. 38). The two are dissimilar, again, in the scope of their respective temporal coverage, the epic being restricted by "no limits in its time of action" where tragedy was traditionally associated with "a complete action" played out during a period of around twenty-four hours (pp. 45, 38). There is considerably more at stake in this genre distinction than the convention of "fear and pity" (p. 48), which has been at times simplistically used as the defining icon of tragedy. Different meters distinguish the various forms considered by Aristotle, the iambic, for example being derived from an association with the "iamb" or lampoon, where heroic hexameter "is the right metre for epic" (p. 67). Stage tragedy employed choral song in lyric meters, with spoken exchanges delivered in tetrameters or iambic trimeters. The notion of "decorum" or appropriateness is rigid in this vision of genre: the "dignified verse" of epic or tragedy being reserved only for those forms, the diction of the latter being modified still further through "the use of expanded, abbreviated and altered forms of words" to "raise the diction above the commonplace" (pp. 63, 65). Contorted language in comedy would, by contrast, prototypically lead to confusion rather than to the thought-provoking—and ultimately fatal—riddle posed by the Sphinx, or indeed those posed by Teiresias to Oedipus in Sophocles' Oedipus the King. Inappropriate usage, in this respect, would challenge audience expectation, were not the classical institutions of literature so rigid in their discouragement of such experimentation.
Aristotle's preoccupation with tragedy in the Poetics has left a corresponding deficiency in the criticism of the lyric, comedy, and, to a considerably lesser extent, epic—criticism of the latter being inevitably colored by the explicit partial congruence with tragedy as well as through Aristotle's discrete pronouncements upon epic stylistics. In consequence, subsequent critics have addressed this imbalance not merely by considering those genre areas specifically but also by developing further the Platonic and Aristotelian canons of genre beyond their apparent boundaries of lyric, comedy, and epic. This expansion and clarification is in many ways retrospective, based as it is in part upon an observation of recurrent textual preoccupations rather than any universally accepted criteria for generation. In contrast to the specific denominations of Platonic and Aristotelian criticism, such developments are frequently termed "classical divisions" or "the classical genres," gaining a certain value—as alleged origins, as touchstones for subsequent work—in consequence.
Access to the specifics of these "classical" genres—and to the vagueness that often surrounds them—might be most conveniently made through what has effectively become a genre in modern criticism itself, the critical handbook marketed at undergraduate readers. Writing in 2002, John Peck and Martin Coyle inform the student reader that "the main generic division today is into poetry, drama and the novel, but in earlier times the major genres were recognised as epic, tragedy, lyric, comedy and satire" (p. 1). Ross Murfin and Supryia M. Ray, writing in 1997, concur, though they offer "pastoral" as an equal to the five "classical" genres. What is apparent, again, is the lack of consensus among critics.
Notable also, however, is the particular valorization of satire as a discrete genre, rather than in its more traditional status in Greek criticism as an element in comedy. Claimed as a uniquely Roman tradition by Quintilian, satire was in Aristotelian terms little more than a base ancestor of comedy or a mere component of that lesser genre. Although its inclusion in a modern tabulation of genres may reflect the acknowledgment of the parallel status of Roman art alongside Greek, it may arguably also be associated with the enhanced status enjoyed by satirical writing in the modern world. The pastoral or "bucolic" genre similarly enjoyed a classical reputation as a component of epic, lyric, or tragedy, though its potential as a discrete genre was established by the Greek poet Theocritus (third century B.C.E.), its conventions being further developed and popularized by the Roman poet Virgil (70–19 B.C.E.). Again, though classical antecedents are undoubtedly important in the establishment of pastoral as a discrete genre, it must be acknowledged that its status in the contemporary critical field is enhanced by the influence of pastoral stylistics upon individual writers from William Shakespeare to Thomas Hardy, and its contribution to literary and critical movements from the Romanticism of the eighteenth and nineteenth centuries to late-twentieth-century ecocriticism. Genre, as it were, may be valued as much for the texts it has inspired indirectly as for its direct generational capacity as a literary matrix.