Journal of the History of Philosophy

According to its author, this book aims at reconstructing key parts of Abelard's logic while denying him a role as a hero of connexive logic or more generally as one of history's greatest logicians. At the end of the preface, we are told that "Abaelard hat die Logik seiner Zeit nicht revolutioniert; er hat keine Kalküle konstruiert; und er hat auch nicht die Logik seiner Zeit auf ein höheres Niveau gehoben" (xiv).

The book is divided into twenty-three chapters with titles such as "'Destruierende' versus 'separierende' Negation," "Vollkommene und unvollkommne Folgerungen," and "'Leere' Begriffe." As the titles show, it ranges over a large field. The results of Lenzen's analyses of Abelard's argumentation are presented in modern logical notation. There are many fine analyses, and despite Lenzen's refusal to see Abelard as a genius, he, too, seems to have been quite impressed by the old logician. However, at the end of the day, I am not sure that I have become any wiser about Abelard's contribution to the history of logic.

Lenzen is a newcomer to the study of twelfth-century logic, and the book is marked by this in several ways. Thus, he informs the reader that "Spätestens seit Prantls Publikation der 'Geschichte der Logik im Abendlande' steht fest, dass Abaelards Traktat 'De Sillogismis Ypoteticis' sich stark an das Werk 'De syllogismo hypothetico' von Boethius (470–524) anlehnt" (165). This is quite true, but anything else would have been very remarkable, so the reference to Prantl serves no purpose.

Unsurprisingly, the main source texts used are Abelard's Dialectica and his Glosae super Peri hermeneias, a part of the series of commentaries on the Ars vetus that go under the common name of Logica ingredientibus. Lenzen displays a cavalier attitude to philology. He quotes the Dialectica from De Rijk's second edition (1970), but in the bibliography he mentions that there are two editions without stating explicitly which one he quotes. In the case of the Glosae, he uses the obsolete editio princeps by Bernhard Geyer from 1927, and he does not even mention its replacement, Klaus Jacobi and Christian Strub's much superior 2010 edition in the series Corpus Christianorum, Continuatio Mediaevalis. This is inexplicable, for in his preface Lenzen describes his book as the child of a research project he began several years after the publication of the new edition. Now, fortunately, the use of Geyer does not have disastrous consequences for Lenzen's interpretation of Abelard, but had he used Jacobi and Strub's edition, he would not have had to propose a textual emendation in one place (88n17), nor would he have needed to quote, in another place, a Latin text (which he does not translate) with a nonsensical significantem instead of figurative (94n1o).

Lenzen sometimes proposes textual emendations, but not always in a perspicuous way, and they are not all felicitous. For example, a quotation of L. M. de Rijk's edition of Introductiones Montane Minores in Logica Modernorum (LM) II.2 (1967) contains the phrase aliquod opposit[or]um (127n2). An unsuspecting reader would think this means De Rijk had conjecturally emended oppositorum into oppositum, for this is what opposit[or]um would mean in LM II.2. In fact, De Rijk just prints oppositum, so Lenzen's opposit[or]um must mean that he wants to correct De Rijk's text by inserting 'or,' but he forgets to tell us that he does not [End Page 520] faithfully reproduce the text quoted and that his square brackets mean something different from what they do in De Rijk's edition. This issue aside, his conjecture is superfluous, as proven by a parallel passage in LM II.2: 118. Similarly, he quotes Abelard as saying "alterum istorum [est]: vel nox vel dies" (152). The "[est]" is Lenzen's own, again superfluous, contribution to the text. By contrast, elsewhere he proposes to insert a non at LM II.2: 64.2. This time, he explains what he is doing, and I think his conjecture...