Page:Catholic Encyclopedia, volume 9.djvu/366

 LOOIO

327

LOOZO

who reveals an acquaintance with the Aristotelean "Organon" in its entirety is John of Salisbury (died 1182), a disciple of Abelard, who explains and defends the legitimate use of dialectic in his work " Metalogi- cus".

The definite triumph of Aristotelean logic in the schools of the thirteenth century was influenced by the introduction into Christian Europe of the com- plete works of Aristotle in Greek. The occasioti of this was the taking of Constantinople by the crusaders in 1204. The Crusades had also the effect of bringing Christian Europe into closer contact with the Arabian scholars who, ever since the ninth century, had culti- vated Aristotelean logic as well as the neo-Platonic interpretation of Aristotle's metaphysics. It was the Arabians who distinguished logica docens and logica tUens, The former is logic as a theoretical science; the latter is lo^c as an applied art, practical logic. To them also is attributed the distinction between first intentions and second intentions. The Arabians, however, did not exert a determining influence on the development of Scholastic logic; they contributed to that development only in an external manner, by helping to make Aristotelean literature accessible to Chnstian thinkers. St. Thomas Aquinas and his teacher. Blessed Albertus Ma^us (Albert the Great), did signal service to Scholastic logic, not so much by adding to its technical rules as by defining its scope and determining the limits of its legitimate applica- tions to theology. They both composed commen- taries on Aristotle's logical works and, besides, wrote independent logical treatises. The work, however, whicn bears the name "Summa Totius Logicffi", and is found among the " Opuscula" of St. Thomas, is now judged to be from the pen of a disciple of his, Herv6 of Nedellac (Hervaeus Natalis). John Duns Scotus was also a commentator on Aristotle's logic. His most important original treatises on logic are " De Univer- sahbus", in which he goes over the ground covered by Porphyry in the " Isa^oge", and " Grammatica Specu- lativa". The latter is an interesting contribution to critical logic.

The tecnnic of logic received special attention from Petrus Hispanus (Pope John XXI, died 1277), author of the * ' SummulaB Logicales' '. This is the first medie- val work to cover the whole eround of Aristotelean logic in an original way. All its predecessors were merely summaries or abridgments of Aristotle's works. In it occur the mnemonic Tines, " Barbara, Celarent", ete., and nearly all the devices of a similar kind which are now used in the study of logic. They are the first of the kind in the history of logic, the lines in the ninth-century MS. mentioned above being verses to aid the memory, without the use of arbitrary signs, such as the designation of types of propositions by means of vowels. And the credit of havingintroduced them is now almost unanimously given to Petrus him- self. The theory that he borrowed them from a Greek work by Psellus (see above) is discredited by an examination of the MSS., which shows that the Greek verses are of later date than those in the " Summul®". In fact, it was the Bvzantine writer who copied the Parisian teacher, and not, as Prantl contended, the Latin who borrowed from the Greek. William of Occam (1280-1349) improved on the arrangement and method of the " Summul®" in his " Summa Totius Logicae". He also made important contributions to the doctrine of supposition of terms. He did not, however, agree witn St. Thomas and Bl. Albert the Great in their definition of the scope and application of logic. His own conception of the purpose of lo^ic was simSciently serious and dignified. It was his followers, the Occamists of the fourteenth and fifteenth cen- turies, who, by their abuse of dialectical methods, brought Scholastic logic into disrepute. One of the most original of all the Scholastic logicians was Ray- mond Lully (1234-1315). In his " Dialegtica" he ex-

pounds clearly and concisely the logic of Aristotle, to*

f ether with the additions made to that science by 'etrus Hispanus. In his " Ars Ma^na", however, he discards all the rules and prescriptions of the formal science, and undertakes oy means of his "logical machine" to demonstrate in a perfectly mechanical way all truth, supernatural as well as natural.

Scholastic logic, as may be seen from this sketeh. did not modify the logic of Aristotle in any essential manner. Nevertheless, the logic of the Schools is an improvement on Aristotelean logic. The School- men made clear many points which were obscure in Aristotle's works: for example, they determined more accurately than he did the nature of logic and its place in the plan of sciences. This was brought about naturally by the exigencies of theological controversy. Moreover, the Schoounen did much to fix the technical meanings of terms in the modern languages, and. though the scientific spirit of the ages that followea spumed the methods of the Scholastic logicians, its own work was very much facilitated by the efforts of the Scholastics to distinguish the significations of words, and trace the relationship of language to thought. Finally, to the Schoolmen logic owes the various memory-aiding contrivances by the aid of which the task of teaching or learning the technicali- ties of the science is greatly facilitated.

G. Modern Logic. — ^The fifteenth century witnessed the first serious attempts to revolt against the Aris- totelean logic of the Schools. Humanists like Ludo- vicus Vico and Laurentius Valla made the methods of the Scholastic logicians the object of their merciless attack on medievalism. Of more importance in tiie history of logic is the attempt of Ramus (Pierre de La Ram6e, 1515-72) to supplant the traditional logic by a new method which he expounded in his works Aris- totelicse Animadversiones and "Scholae Dialecticae". Ramus was imitated in Ireland by George Downame (or Downham), Bishop of Deny, in the seventeenth century, and in the same century he had a most dis- tinfuiaied follower in England in the person of John Milton, who, in 1672, published " Artis Logicse Plenior Institutio ad Petri Rami Methodum CSoncinnata". Ramus 's innovations, however, were far from receiving universal approval, even amonjg Protestants. Me- lanchthon's *^ Erotemata Dialectica", which was sub- stantially Aristotelean, was extensively used in the ProtestaJit schools, and exerted a wider mfluence than Rjunus's "Animadversiones". Francis Bacon (1561- 1626) inaugurated a still more formidable onslaught. Profiting by the hints thrown out by his countryman and namesake, Roger Bacon (1214-1294), he attacked the Aristotelean method, contending that it was utterly barren of results in science, that it was, in fact, essen- ti^y unscientific, and needed not so much to be re- formed as to be entirely supplanted by a new method. This he attempted to do m his "Novum Or^anum", which was to introduce a new logic, an inductive logic, to take the place of the deductive logic of Aristotle and the Schoolmen. It is now recognized even by the partisans of Bacon that he erred in two respects. He eired in describing Aristotle's logic as exclusively de- ductive, and he erred in claiming for the inductive method the ability to direct the mind in scientific discovery and practical invention. Bacon did not succeed in overthrowing the authority of Aristotle. Neither did Descartes (1596-1649), who was as desir- ous to make logic serve the purposes of the mathemar tician as Bacon was to make it serve the cause of scientific discovery. The Port Royal Logic (' 'L' Art de penser", 1662), written by Descartes's disciples, is essentially Aristotelean. So, though in a less degree, are the logical treatises of Hobbes (1588-1679) and Gassendi (1592-1655), both of whom underwent the influence of Bacon's ideas. In the seventeenth and eighteenth centuries. Father BufiSer, Le Clero (Clericus), Wolff, and Lambert strove to modify the Aristotelean