 Another point worth mentioning is the fact that medieval discussions of the concept of consequence cover both what we would now describe as ‘philosophy of logic’ and as ‘logic proper’. As for the latter, a number of medieval authors such as Abelard (Martin 2004), Burley (De Puritate), and Buridan (TC) formulated rules of inference and proved theorems about them (Klima 2016). Many authors had for the most part understood the logical behavior of what we now view as the main sentential/propositional operators, such as ‘if…then’, ‘or’, negating terms, as well as meta-level rules such as the transitivity of consequence, ‘from the impossible anything follows’, or ‘the necessary follows from anything’ (the latter two were however not unanimously endorsed — see (Martin 1986), (Read 1993, 2010)). (For discussions of the rules formulated by different authors, see (Pozzi 1978), (Boh 2001), (Dutilh Novaes 2008)). They also offered sophisticated investigations of the logical behavior of e.g. modal terms (Buridan, TC) (Johnston 2014).