First comes demonstration. Knowledge of demonstration is necessary for reliable scientific knowledge and for the discernment of fallacious arguments. But it is noteworthy that Galen envisages two possible pathways for this first phase of the curriculum (Ord. Lib. Prop. 1–2). For one who aspires to true knowledge, a thorough grounding in Galen’s logical magnum opus, Demonstration, is essential. But there is a more practical compromise: the less logically ambitious or adept may—taking as his starting-point the “introductory” methodological work, Sects for Beginners (SI)—proceed to the next stage without that thorough grounding. Some logical training is envisaged here too; but Galen is optimistic about the ability of the non-philosophical layperson to arrive at the truth on the basis of common conceptions and a basic ability to follow arguments (such ability being contrasted with the tendency of sectarian philosophers to create or succumb to sophistic fallacies); key here is that the person in question should have acquired a solid education in the traditional Greek “fundamentals”, which involved mathematics and logic (Aff. Pecc. Dig. II.3; Lib. Prop. preface). But this latter person will—following a Platonic distinction—only be able to aspire to correct opinion, not to secure knowledge.