 Abelard gives the four standard figures and shows how the second, third, and fourth (he treats the fourth figure as part of the first figure with the terms in the conclusion converted) can be reduced to the first in the standard ways using conversion rules and proofs through impossibility, but to clarify and simply the theory he also presents rules showing the validity of the different moods. In the first figure he gives these rules (I have included the terms A, B, C to clarify the rules, though they are not in Abelard’s text):