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with the question of the criterion of truth, which is still an important problem in major logic, or. as it is now called, epistemology. Undoubtedly, tney im- proved on Aristotle's logic in many points of detail; but to what extent, and in what respect, is a matter of oonjectme, owing to the loss of the voluminous Stoic treatises on logic. Their rivals, the Epicmeans (see Epicureanism) professed a contempt for logic — or "canonic", as they styled it. They maintedned that it is an adjunct of physics, and that a knowledge of physical phenomena acquired through the senses is the only knowledge that is of value in the pursuit of happi- ness. After the Stoics and the Epicureans came the commentators. These may, for convenience, be divided into the Greeks and the Latins. The Greeks, from Alexander of Aphrodisias, in the second, to St. John of Damascus in the eighth century of our era, flourished at Athens, at Alexandria, and in Asia Minor. With Photius, in the ninth century, the scene is shifted to Constantinople. To the first period belong Alexan- der of Aphroaisias, known as "the Commentator", Themistius, David the Armenian, Philoponus, Simpli- cius. and Porphyrv, author of the Isagoge (Eurayuyiff) , or "Introduction to the logic of Aristotle. In this work the author, by his explicit enumeration of the five prcdicables and his comment thereon, flung a challenge to the medieval logicians, which they took up in the famous controversy concerning universals ^ee Universals). To the second period belong Photius, Michael Psellus the younger (eleventh cen- tuir), Isicephorus Blemmydes. George Pachymeres, and Leo Magentinus (thirteenth century). All these did little more than abridge, explain, and defend the text of the Aristotelean works on logic. An exception should, perhaps, be made in favour of the physician Galen (second century), who is said to have introduced the fourth syllogistic figure, and who wrote a special work, " On Fallacies of Diction".

E. Lalin Commentators, — ^Among the Latin com- mentators on Aristotle we find almost in every case more originahty and more inchnation to add to the science of logic than we do in the case of the Greeks. After the taking of Athens by Sulla (84 b. c.) the works of Aristotle were carried to Rome, where they were arranged and edit^Ml by Andronicus of Rhodes (see Aristotle). The first logical treatise in Latin is Cicero's abridgment of the "Topics". Then came a long period of inactivity. About a. d. 160, Apuleius wrote a short account of the "Interpretation". In the middle of the fourth century Marius Victorinus translated Porphyry's " Isagoge". To the time of St. Augustine belong the treatises ^'Categoria? Decem" and " Principia Dialectica". Both were attributed to St. Augustine, though the first is certainlv spurious, and the second of doubtful authenticity, rf hey were very often transcribed in the early Middle Ages, and the logical treatises of the ninth and tenth centuries make very free use of their contents. The most popular, however, of all the Latin works on logic was the curious medley of prose and verse "De Nuptiis Mer- curii et Philologiaj' by Marcianus Capella (about a. d. 475). In it dialectic is treated as one of the seven liberal arts (see Arts, The Seven Liberal), and that portion of the work was the text in all the early medie- val schools of logic. Another writer on logic who exerted a widespread influence during the first period of Scholasticism was Boethius (470-524), who wrote two commentaries on the " Isagoge" of Porphyry, two on Aristotle's " Interpretation", and one on the " Cate- «>ries' ' . Besides, he wrote the original treatises, " On Categorical Syllogisms", "On Division", and "On Topical Differences", and translated several portions of Aristotle's logical works. In fact, it was princi- pally through his translations that the early Scholastic writers, who as a rule, were entirely ignorant of Greek, had access to Aristotle's writings. Cassiodorus, a contemporary of Boethius, wrote a treatise, " On the

Seven Liberal Arts", in which, in the portion devoted to dialectic, he gave a summary and analvsis of the Aristotelean ana Porphyrian writings on logic. Isi- dore of Seville (died 636), Venerable Bede (673-735), and Alcuin (736-804), the forerunners of the Scholas- tics, were content with abridging in their logical works the writings of Boethius and Cassiodorus.

F. The Scholastics. — ^The first masters of the schools in the age of Charlemagne and the century immedi- ately following were not acquainted at first hand with Aristotle's works. They used the works and transla- tions of Boethius, the pseudo-Augustinian treatises mentioned above, and the work by Marcianus Capella. Little by little tneir interest became centred on the metaphysical and psychological problems suggested in those treatises, especially on the problem of univer- sals and the conflict between ReaUsm and Nominalism. As a consequence of this shifting of the centre of inter- est, very little was done towards perfecting the technic of logic, and there is a very noticeable dearth of original work during the ninth and tenth centuries. John Scotus Eriugena, Eric and Remi of Auxerre, and the teachers at St. Gall in Switzerland confined their activity to glossing and commenting on the traditional texts, especially Pseudo-Augustine and Marcianus Capella. In the case of the St. Gall teachers we have however, by way of exception, a work on logic (pub- lished by Piper, " Die Schriften Notkers", I, Freiburg, 1895), which bears evident traces of the influence of Eriugena, and a collection of mnemonic verses con- taining the nineteen valid syllogisms (published from ninth-century MS. in the "Philosophical Review", Sept., 1907, XVI, 5).

Roscelin (about 1050-1100), by his outspoken pro- fession of Nominalism, concentrated the attention of his contemporaries and immediate successors on the problem of universals. In the disciission of that problem the art of dialectical disputation was devel- oped, and a taste for argumentation was fostered, but none of the dialecticians of the twelfth century, with the exception of Abelard, contributed to the advance- ment of the science of logic. This Abelard did in several ways. In his work to which Cousin gave the title "Dialectica", and in his commentaries, he strove to widen the scope and enhance the utility of logic as a science. Not only is it the science of disputation, but also the science of discovery, by means of which the arguments supplied by a study of nature are examined. The principal application of logic, however, is in the discussion of rehgious truth. Here Abelard, citing the authority of St. Augustine, contends that the methods of dialectic are applicable to the discussion of all truth, revealed as well as rational; they are appli- cable even to the mysteries of faith. In -principle he was right, although in practice he went further than the example of St. Augustine would warrant him in going. His subsequent condemnation had for its ground, not the use of dialectic in theology, but the excessive use of dialectic to the point of rationalism. Abelard, it should be noted, was acquainted only with those treatises of Aristotle which had been translated bv Boethius, and which constituted the logica vetus. ilis contemporary, Gilbert de la Porr^e (q. v.), added to the old logic a work entitled "Liber Sex Princi- piorum", a treatise on the last six of the Aristotelean Categories. Towards the middle of the twelfth cen- tury the remainder of the Aristotelean "Organon" became known, so that the logic of the schools, thenceforth known as logica nova, now contained: (1) Aristotle's "Categories" and "Interpretation" and Porphyry's " Isagoge" (contents of the logica vetus); (2) Aristotle's "Analvtics", "Topics", and "Sophisms"; (3) Gilbert's "Liber Sex Pnncipiorum". This was the text in the schools when St. Thomas began to teach, and it continued to be used until superseded by the logica modemay which embodied the contributions of Petrus Hispanus. The first writer of importance