 Sections  2  and  3  discuss these two tasks in that order. For now, the basic idea can be conveyed using the example of the self-referential sentence \(k\) that reads “If \(k\) is true then time is infinite”. First, given our understanding of truth, we recognize that the sentence “\(k\) is true” is intersubstitutable with “If \(k\) is true, then time is infinite”. Second, the informal argument of  section 1.1  derives a paradoxical conclusion from this equivalence. Readers chiefly interested in the logical principles involved in that argument and related ones, and the options for resisting such arguments, may wish to turn to  section 3.