 The entire edifice of Avicenna’s connective syllogistic rests on the assumption that certain argument forms are self-evidently productive (bayyina, bayyina bi-anfusihā, bayyinat al-intāğ) or perfect (kāmila) and that all other forms can be reduced (ruğūʿ) to them by standard methods of proof. The latter include (i) proofs based on conversion (ʿaks) (alongside other kinds of transformation of premises or conclusions into logically equivalent premises or conclusions, in the case of hypothetical syllogisms), (ii) proofs based on setting out a term (iftirāḍ)—the counterpart of the Aristotelian notion of ecthesis, and (iii) proofs through the impossible (or reductio ad absurdum, qiyās al-ḫalf). Depending on the circumstances, one, two or all three methods may be used to prove productivity.