Early in his presentation, Avicenna considered whether the absolute e-proposition, “no J is B”, converts to “no B is J” (a conversion accepted by his predecessors and contemporaries). Avicenna rejected absolute e-conversion and offered a counter-example found in Aristotle, “no horse is sleeping” (Avicenna Najât [1985] 39), and one of his own, “no man is laughing” (Avicenna Ishârât [1971] 322). He accepted that absolute a- and i-propositions convert: