This chapter examines the methods to acquire knowledge. The methods considered are the analytic method, the analytic-synthetic method, the material axiomatic method, and the formal axiomatic method. The chapter also examines the original formulation of these methods, and the relations between them. Since deductive and non-deductive rules play a crucial role in the methods in question, the chapter discusses which of these rules are ampliative, in the sense that the conclusion is not contained in the premisses.