Imagine a community commonly believing: “Every traditional medicine benefits every patient.” Someone argues: “This is a traditional medicine; therefore it benefits every patient.”
Even if the inference has a valid universal-to-particular form, its major premise has not been established as true. The difficulty lies in the matter, not necessarily the formal arrangement.
This is a supplementary illustration, not a quotation from the book. It shows why dialectical use must not be conflated with demonstrative proof.