Abbo of Fleury (940/45-1004) was the first medieval author to deal with Boethius' De Syllogismis Hypotheticis. However he must have used a former source on the so-called 'undemonstrable' hypothetical syllogisms, which has been lost in later centuries.
Abbo's treatise shows that its author was not only passing on ancient doctrines (which at any rate were new to his century) but was at least reorganizing his material in an original way and developing some doctrines just hinted at by Boethius.
Abbo of Fleury seems to have been the only medieval logician to realize that there exists an internal link between the doctrine of hypothetical syllogism contained in Boethius' treatise on this subject and the doctrine of the famous seven 'indemonstrable' syllogisms. This is an important systematic insight, even if Abbo's attempt at unifying both doctrines was only partially successful. It opens once again the historical and systematic question about the relationship and the difference between stoic and peripatetic propositional logic. This volume provides the first critical edition of Abbo of Fleurys De Syllogismis Hypotheticis, together with a German translation, an introduction and an extensive commentary.