Aside from the First Vintage and the Instances with Special Powers, Bacon enumerates additional "aids to the intellect" which presumably are the next steps in his "method." In Aphorism 21 of Book II, Bacon lays out the subsequent series of steps in proper induction: including Supports to Induction, Rectification of Induction, Varying the Inquiry according to the Nature of the Subject, Natures with Special Powers, Ends of Inquiry, Bringing Things down to Practice, Preparatives to Inquiry and Ascending and Descending Scale of Axioms. These additional aids, however, were never explained beyond their initial limited appearance in Novum Organum.