The chapter explains two fundamental roots of error: failure to understand and mistaking falsehood for truth because of resemblance. A unifying diagnosis is the failure to distinguish a thing from what resembles it.
Verbal ambiguity occurs both in single terms and in composed expressions. Equivocation, metaphor, morphology, vowels, pointing, pronoun reference, and the joining or separation of predicates have different causes, but each can undermine the continuity of meaning within an argument.
The next section treats fallacies arising from meaning, where a proposition or syllogism can be defective even when its words are understood correctly.