  The second question is that of a metatheory. Here the story becomes somewhat more complicated. There was a generally accepted metatheory, namely that of Aristotle’s Posterior Analytics, according to which scientific demonstrations were syllogistic proofs, based on necessary and self-evident premises. There were two sorts of these: proofs of the simple fact (demonstrationes quia) and proofs of the reasoned fact (demonstrationes propter quid). In the latter, the syllogisms involved must have middle terms that are causes of the state of affairs which is to be demonstrated. This gives a theory of scientific reasoning in which the structure of the arguments is intimately tied up with the structure of the causal chains that they demonstrate.