Realism has not only shaped important schools and periods in literary history, but has also been a fundamental constant of all literature, its first theoretical formulation being the principle of mimesis in Aristotle's Poetics. Realism can be considered by extension one of the main aspects of literary theory, the aims of which must be to define its concepts clearly and to neutralize the imprecision, polysemy, and ambiguity that often characterized the application of realism.