 Retracing the historical sources for the development of this notion would take us too far afield, but it seems that the emergence of the idea of ‘following of necessity’ is closely related to dialectical practices of debates (Dutilh Novaes 2021), both in philosophy/logic (Castelnérac and Marion 2009) and in mathematics (Netz 1999). But while it is a necessary condition, necessary truth-preservation is notoriously not a sufficient condition for syllogistic validity. For example, as is well known, Aristotle’s syllogistic does not validate the principle of reflexivity, i.e., ‘A implies A’ for any sentence A, even though this principle is the most transparent occurrence of necessary truth-preservation one can think of. Instead, it seems that syllogistic validity requires a great deal more to hold (Thom 2010) (Thom 2016). Interestingly, Aristotle himself suggests that the premises in a syllogism are the material causes for the conclusion (Metaphysics 1013b19–20; Physics 195a18–19), “in the sense of ‘that from which’”, thus somewhat in the spirit of the idea of premises containing the conclusion expressed in (Co), and more generally the idea that the antecedent is the cause of the consequent (which would become widespread in the 13th century (Spruyt 2018)). Indeed, it has been claimed that