CriticaLink | Aristotle: Poetics | Guide to Book XXV
Faults in poetic works can be organized into two general categories: essential faults that impair the work as a while and accidental faults, such as factual errors, that may be irritating, distracting, and disappointing, but do not indicate a failure of artistic skill. Book XXV goes on to cover five sub-categories of faulty representation: impossibility, irrationality, moral harmfulness, contradiction, and failure to conform to artistic rules.
All errors should be avoided, Aristotle asserts, but he seems interested in establishing fair conditions for criticism. Throughout this chapter, he reflects on ways each of the five criticisms might be refuted, stressing that critics must always bear in mind the self-consistency and purpose of the work as a whole. Aristotle does not appear to address these errors in any particular order, and does not directly address the issue of moral harm. His remarks on the remaining categories are as follows:
Contradiction When we meet with apparent contradictions in a work of art, we must apply careful methods of analysis to determine whether the word or phrase that seems to contradict an earlier expression in fact has the meaning we are assigning it. Aristotle suggests that we credit the author with enough intelligence to avoid blatant contradiction until we are convinced that the inconsistency is in fact a mistake and not an artistic strategy.
Failure to Conform to Artistic Rules
Careful attention to the way a poet is using language may reveal that an phrase or passage that appears confusing or nonsensical is in fact metaphorical, or intentionally ambiguous, or has some other function in supporting the representation.