  Following Aristotle and Porphyry, Buridan's logic is based on two distinct, but complementary, conceptions of its purpose: theoretical or pedagogical (logica docens) and practical (logica  utens).[13]  The former, he says, is so called because “it teaches [docet] us how, and from what [materials], arguments should be constructed, whether those arguments be demonstrative, dialectical, or of some other kind”. The latter takes its name from the fact that “it uses [utitur] arguments in order to prove whether some conclusion is evident, regardless of the subject matter of the conclusion” (QIP 1: 126–7, ll.176–80). But since the teaching of logic is ordained to its use, Buridan holds that logic is ultimately a practical rather than a speculative discipline.