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Aristotle (384-322B.C.) is known as the founder of Logic. In the six treatises which he devoted to the subject, Aristotle examined and analysed the thinking processes for the purpose of formulating the laws of thought.
These treatises are "The Categories", "Interpretation", "Prior Analytics", "Posterior Analytics", "Topics", and "Sophisms". These were afterwards given the title of "Organon", or "Instrument of Knowledge"; this designation, however, did not come into common use until the fifteenth century.
The first four treatises contain, with occasional excursions into the domain of grammar and metaphysics, the science of formal logic essentially the same as it is taught at the present day. The "Topics" and the "Sophisms" contain the applications of logic to argumentation and the refutation of fallacies. In conformity with the fundamental principle of his theory of knowledge, namely, that all our knowledge comes from experience, Aristotle recognizes the importance of inductive reasoning, that is to say, reasoning from particular instances to general principles. If he and his followers did not develop more fully this portion of logic, it was not because they did not recognize its importance in principle. His claim to the title of Founder of Logic has never been seriously disputed the most that his opponents in the modern era could do was to set up rival systems in which induction was to supplant syllogistic reasoning. One of the devices of the opponents of scholasticism is to identify the Schoolmen and Aristotle with the advocacy of an exclusively deductive logic.
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The history of logic possesses a more than ordinary interest, because, on the one hand, every change in the point of view of the metaphysician and the psychologist tended to produce a corresponding change in logical theory and practice, while, on the other hand, changes in logical method and procedure tended to affect the conclusions as well as the method of the philosopher. Notwithstanding these tendencies towards variation, the science of logic has undergone very few radical changes from the beginning of its history.
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The Nyaya is a system of philosophy which was studied in India in the fifth century B.C., though it is perhaps, of much older date, takes its name from the word nyaya, meaning logical argument, or syllogism. This philosophy, like all the Indian systems, busied itself with the Problem of the deliverance of the soul from bondage, and its solution was that the soul is to be freed from the trammels of matter by means of systematic reasoning. This view of the question led naturally to an analysis of the methods of thinking, and to the construction of a type of reasoning which bears a remote resemblance to the syllogism. The nyaya, or Indian syllogism, as it is sometimes called, consists of five propositions. If, for instance, one wishes to prove that the hill is on fire, one begins with the assertion: "The hill is on fire." Next, the reason is given: "For it smokes." Then comes an instance, "Like the kitchen fire"; which is followed by the application, "So also the hill smokes." Finally comes the conclusion, "Therefore it is on fire." Between this and the clear-cut Aristotelean syllogism, with its major and minor premises and conclusion, there is all the difference that exists between the Oriental and the Greek mode of thinking. It is hardly necessary to say that there is no historical evidence that Aristotle was in any way influenced in his logic by Gotama, the reputed author of the nyaya.
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The first philosophers of Greece devoted attention exclusively to the problem of the origin of the universe. The Eleatics, especially Zeno of Elea, the Sophists, and the Megarians developed the art of argumentation to a high degree of perfection. Zeno was especially remarkable in this respect, and is sometimes styled the Founder of Dialectic. None of these, however, formulated laws or rules of reasoning. The same is true of Socrates and Plato, although the former laid great stress on definition and induction, and the latter exalted dialectic, or discussion, into an important instrument of philosophical knowledge.
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Among the immediate disciples of Aristotle, Theophrastus and Eudemus devoted special attention to logic. To the former is sometimes attributed the invention of the hypothetical syllogism, although the same claim is sometimes made for the Stoics. The latter, to whom, probably, we owe the name logic, recognized this science as one of the constitutive parts of philosophy. They included in it dialectic and rhetoric, or the science of argumentation and the science of persuasion. They busied themselves also 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, they improved on Aristotle's logic in many points of detail; but to what extent, and in what respect, is a matter of conjecture, owing to the loss of the voluminous Stoic treatises on logic. Their rivals, the Epicureans professed a contempt for logic-or "canonic", as they styled it. They maintained 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 happiness. 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 Alexander of Aphrodisias, known as "the Commentator" Themistius, David the Armenian, Philoponus, Simplicius and Porphyry, author of the Isagoge (Eisagoge), or "Introduction" to the logic of Aristotle. In this work the author, by his explicit enumeration of the five predicables and his comment thereon, flung a challenge to the medieval logicians, which they took up in the famous controversy concerning universals. To the second period belong Photius, Michael Psellus the younger (eleventh century), Nicephorus 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".
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Among the Latin commentators on Aristotle we find almost in every case more originality and more inclination 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 edited by Andronicus of Rhodes. 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 "Categoriae Decem" and "Principia Dialectica". Both were attributed to St. Augustine, though the first is certainly spurious, and the second of doubtful authenticity. They 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 Mercurii et Philologiae" by Marcianus Capella (about A. D. 475). In it dialectic is treated as one of the seven liberal arts and that portion of the work was the text in all the early medieval 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 "Categories". 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 principally 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 analysis of the Aristotelean and Porphyrian writings on logic. Isidore of Seville (died 636), Venerable Bede (673-735) and Alcuin (736-804), the forerunners of the Scholastics, were content with abridging in their logical works the writings of Boethius and Cassiodorus.
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Scholastic logic did not modify the logic of Aristotle in any essential manner. Nevertheless, the logic of the Schools is an improvement on Aristotelean logic. The Schoolmen 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 Schoolmen did much to fix the technical meanings of terms in the modern languages, and, though the scientific spirit of the ages that followed spurned 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 technicalities of the science is greatly facilitated.
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The fifteenth century witnessed the first serious attempts to revolt against the Aristotelean logic of the Schools. Humanists like Ludovicus Vico and Laurentius Valla made the methods of the Scholastic logicians the object of their merciless attack on medievalism. Of more importance in the history of logic is the attempt of Ramus (Pierre de La Ramee, 1515-72) to supplant the traditional logic by a new method which he expounded in his works "Aristotelicae Animadversiones" and "Scholae Dialecticae". Ramus was imitated in Ireland by George Downame (or Downham), Bishop of Derry, in the seventeenth century, and in the same century he had a most distinguished follower in England in the person of John Milton, who, in 1672, published "Artis Logicae Plenior Institutio ad Petri Rami Methodum Concinnata". Ramus's innovations, however, were far from receiving universal approval, even among Protestants. Melanchthon's "Erotemata Dialectica", which was substantially Aristotelean, was extensively used in the Protestant schools, and exerted a wider influence than Ramus'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, essentially unscientific, and needed not so much to be reformed as to be entirely supplanted by a new method. This he attempted to do in his "Novum Organum", 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 erred in describing Aristotle's logic as exclusively deductive, 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 desirous to make logic serve the purposes of the mathematician 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 Buffier, Le Clerc (Clericus), Wolff, and Lambert strove to modify the Aristotelean logic in the direction of empiricism, sensism, or Leibnizian innatism. In the treatises which they wrote on logic there is nothing that one might consider of primary importance.
Kant and the other German Transcendentalists of the nineteenth century took a more equitable view of Aristotle's services to the science of logic. As a rule, they recognized the value of what he had accomplished and, instead of trying to undo his work, they attempted to supplement it. It is a question, however, whether they did not do as much harm to logic in one way as Bacon and Descartes did in another. By withdrawing from the domain of logic what is empirical, and confining the science to an examination of "the necessary laws of thought", the Transcendentalists gave occasion to Mill and other Associationists to accuse logic of being unreal, and out of touch with the needs of an age which was, above all things, an age of empirical science. Most of the recent German literature on logic is characterized by the amount of attention which it pays either to historical inquiries, or to inquiries into the value of knowledge, or to investigation of the philosophical foundations of the laws of logic. It has added very little to the technical portion of the science. In England, the most important event in the history of logic in the nineteenth century was the publication, in 1843, of John Stuart Mill's "System of Logic". Mill renewed all the claims put forward by Bacon, and with some measure of success. At least, he brought about a change in the method of teaching logic at the great English seats of learning. Carrying Locke's empiricism to its ultimate conclusion, and adopting the association theory of the human mind, he rejected all necessary truth, discarded the syllogism as not only useless but fallacious, and maintained that all reasoning is from particulars to particulars. He did not make many converts to these views, but he succeeded in giving inductive logic a place in every textbook on logic published since his time. Not so successful was the attempt of Sir William Hamilton to establish a new logic (the "new analytic"), on the principle that the predicate as well as the subject of a proposition should be quantified. Nor, indeed, was he quite original in this: the idea had been put forward in the seventeenth century by the Catholic philosopher Caramuel (1606-82). Recent logical literature in English has striven above all things to attain clearness, intelligibility, and practical utility in its exposition of the laws of thought. Whenever it indulges in speculation as to the nature of mental processes, it is, of course, coloured by the various philosophies of the time.
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Indeed, the history of logic is interesting and profitable chiefly because it shows how the philosophical theories influence the method and the doctrine of the logician. The empiricism and sensism of the English school, descending from Hobbes through Locke, Hume, and the Associationists, could lead in logic to no other conclusion than that to which it does lead in Mill's rejection of the syllogism and of all necessary truth. On the other hand, Descartes's exaltation of deduction and Leibniz's adoption of the mathematical method have their origin in that doctrine of innatism which is the opposite of empiricism. Again, the domination of industrialism, and the insistence for recognition on the part of the social economist, have had in our own day the effect of pushing logic more and more towards the position of a purveyor of rules for scientific discovery and practical invention. The materialism of the last half of the nineteenth century demanded that logic prove its utility in a practical way. Hence the prominence given to induction. But, of all the crises through which logic has passed, the most interesting is that which is known as the "Storm and Stress of Scholasticism", in which mysticism on the one side rejected dialectic as "the devil's art", and maintained that "God did not choose logic as a means of saving his people", while rationalism on the other side set no bounds to the use of logic, going so far as to place it on a plane with Divine faith. Out of this conflict issued the Scholasticism of the thirteenth century, which gave due credit to the mystic contention in so far as that contention was sound, and at the same time acknowledged freely the claims of rationalism within the limits of orthodoxy and of reason. St. Thomas and his contemporaries looked upon logic as an instrument for the discovery and exposition of natural truth. They considered, moreover, that it is the instrument by which the theologian is enabled to expound, systematize, and defend revealed truth. This view of the theological use of logic is the basis for the charge of intellectualism which Modernist philosophers imbued with Kantism have made against the Scholastics. Modernism asserts that the logical nexus is "the weakest link" between the mind and spiritual truth. So that the contest waged in the twelfth century is renewed in slightly different terms in our own day, the application of logic to theology being now, as then, the principal point in dispute.
Editor: Haselhurst
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1. Catholic Encyclopedia: Logic, 1910
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