The president requested me to deliver nine lectures upon the history of logic. I have limited the subject to British Logicians, but even with this limitation I have a subject which would require for an adequate treatment not less than ten times the number of lectures I have to give. I am under the necessity therefore of treating it in an altogether fragmentary manner and you must not be surprized that I leave quite out of account some of the most famous names.

Let it be understood in the first place that I do not come here to air my own opinions or even to talk about logic at all but purely and solely about a branch of history,--the history of logical thought in the British Islands. In such imperfect manner as the time will allow I shall endeavor to show you how this subject appeared to the chief thinkers in England and reproduce their state of mind. But whether they were right or wrong will be for you and me a question altogether to be neglected, for that is a question of philosophy and not of history.

This history of logic is not altogether without an interest as a branch of history. For so far as the logic of an age adequately represents the methods of thought of that age, its history is a history of the human mind in its most essential relation,--that is to say with reference to its power of investigating truth. But the chief value of the study of historical philosophy is that it disciplines the mind to regard philosophy in a cold and scientific eye and not with passion as though philosophers were contestants.

British Logic is a subject of some particular interest inasmuch as some peculiar lines of thought have always been predominant in those islands, giving their logicians a certain family resemblance, which already begins to appear in very early times. The most striking characteristic of British thinkers is their nominalistic tendency. This has always been and is now very marked. So much so that in England and in England alone are there many thinkers more distinguished at this day as being nominalistic than as holding any other doctrines. William Ockham or Oakum, an Englishman, is beyond question the greatest nominalist that ever lived; while Duns Scotus, another British name, it is equally certain is the subtilest advocate of the opposite opinion. These two men Duns Scotus and William Ockham are decidedly the greatest speculative minds of the middle ages, as well as two of the profoundest metaphysicians that ever lived. Another circumstance which makes Logic of the British Islands interesting is that there more than elsewhere have the studies of the logic of the natural sciences been made. Already we find some evidence of English thought running in that direction, when we meet with that singular phenomenon Roger Bacon,--a man who was scientific before science began. At the first dawn of the age of science, Francis Bacon wrote that professedly and really logical treatise the Novum Organum, a work the celebrity of which perhaps exceeds its real merits. In our own day, the writings of Whewell, Mill, and Herschel afford some of the finest accounts of the method of thought in science. Another direction in which logical thought has gone farther in England than elsewhere is in mathematico-formal logic,--the chief writers on which are Boole, De Morgan, and the Scotch Sir Wm. Hamilton,--for although Hamilton was so bitter against mathematics, that his own doctrine of the quantified predicate is essentially mathematical is beyond intelligent dispute. This fondness for the formal part of logic already appeared in the middle ages, when the nominalistic school of Ockham--the most extremely scholastic of the scholastics--and next to them the school of Scotus--carried to the utmost the doctrines of the Parva Logicalia which were the contribution of those ages to this branch of the science. And those Parva Logicalia may themselves have had an English origin for the earliest known writer upon the subject--unless the Synopsis be attributed to Psellus--is an Englishman, William of Sherwood.

You perceive therefore how intimately modern and medieval thought are connected in England--more so than in Germany or France; and therefore how indispensible it is that we should begin our history at a very early date. But here comes a stupendous difficulty. If I were to devote the whole of my nine lectures to medieval philosophy I could not enable you to read a page of Scotus or of Ockham understandingly nor even give you a good general idea of their historical position. I shall content myself therefore with some remarks upon their nominalism and realism with special reference to their relations to modern doctrines concerning generals. And as preliminary to those remarks I will in this lecture give a very slight sketch of the great strife between the nominalists and realists which took place in the 12th century.

All real acquaintance with Scholasticism died out in the 17th century, and it was not till late in our own that the study of it was taken up again. Even now the later ages are little understood but the great logical controversies of the 12th century have been pretty well studied. Cousin began the investigation, by publishing some logical works of Abaelard, together with other works which he wrongly attributed to the author, and by writing an introduction to them in which he gave his conception of the dispute. These contributions of Cousin are contained in his Ouvrages Inédits d'Abélard, which forms one of the volumes of the Documents relatives à l'Histoire de France and in the second edition of his Fragments Philosophiques: Philosophie Scholastique. Hauréau in his Histoire de la philosophie scholastique, de Rémusat in his Abélard, Jourdain in his Recherches critiques sur la connaissance d'Aristote dans le moyen age, and Barach in his Nominalismus vor Roscellinus have brought to light other important documents relative to this subject. The works of Anselm, John of Salisbury, and Alanus of Lille, the Liber sex principiorum of Gilbertus, the same author's commentary on the three books De Trinitate falsely attributed to Boethius, and Abaelard's letters to Heloise and his Introductio in Theologiam--works having an important bearing upon this part of logical history--were already in our possession. The best account of the dispute is contained in Prantl's great Geschichte der Logik im Abendlande, chapter 14.

The most striking characteristic of medieval thought is the importance attributed to authority. It was held that authority and reason were two coördinate methods of arriving at truth, and far from holding that authority was secondary to reason, the scholastics were much more apt to place it quite above reason. When Berengarius in his dispute with Lanfranc remarked that the whole of an affirmation does not stand after a part is subverted, his adversary replied: "The sacred authorities being relinquished you take refuge in dialectic, and when I am to hear and to answer concerning the ministry of the Faith, I prefer to hear and to answer the sacred authorities which are supposed to relate to the subject than dialectical reasons." To this Berengarius replied that St. Augustine in his book De doctrina christiana says that what he said concerning an affirmation is bound up indissolubly with that very eternity of truth which is God. But added "Maximi plane cordis est, per omnia ad dialecticam confugere, quia confugere ad eam ad rationem est confugere, quo qui non confugit, cum secundum rationem sit factus ad imaginem Dei, suum honorem reliquit, nec potest renovari de die in diem ad imaginem Dei." Next to sacred authorities--the Bible, the church, and the fathers,--that of Aristotle of course ranked the highest. It could be denied, but the presumption was immense against his being wrong on any particular point.

Such a weight being attached to authority,--a weight which would be excessive were not the human mind at that time in so uneducated a state that it could not do better than follow masters since it was totally incompetent to solve metaphysical problems for itself,--it follows naturally that originality of thought was not greatly admired but that on the contrary the admirable mind was his who succeeded in interpreting consistently the dicta of Aristotle, Porphyry, and Boethius. Vanity, therefore, the vanity of cleverness was a vice from which the schoolmen were remarkably free. They were minute and thorough in their knowledge of such authorities as they had, and they were equally minute and thorough in their treatment of every question which came up.

All these characters remind us less of the philosophers of our day than of the men of science. I do not hesitate to say that scientific men now think much more of authority than do metaphysicians; for in science a question is not regarded as settled or its solution as certain until all intelligent and informed doubt has ceased and all competent persons have come to a catholic agreement, whereas 50 metaphysicians each holding opinions that no one of the other 49 can admit, will nevertheless severally regard their 50 opposite opinions as more certain than that the sun will rise tomorrow. This is to have what seems an absurd disregard for others' opinions; the man of science attaches a positive value to the opinion of every man as competent as himself so that he cannot but have a doubt of a conclusion which he would adopt were it not that a competent man opposes it; but on the other hand, he will regard a sufficient divergence from the convictions of the great body of scientific men as tending of itself to argue incompetence and he will generally attach little weight to the opinions of men who have long been dead and were ignorant of much that has been since discovered which bears upon the question in hand. The schoolmen however attached the greatest authority to men long since dead and there they were right for in the dark ages it was not true that the later state of human knowledge was the most perfect but on the contrary. I think it may be said then that the schoolmen did not attach too much weight to authority although they attached much more to it than we ought to do or than ought or could be attached to it in any age in which science is pursuing a successful and onward course--and of course infinitely more than is attached to it by those intellectual nomads the modern metaphysicians, including the positivists. In the slight importance they attached to a brilliant theory, the schoolmen also resembled modern scientific men, who cannot be comprehended in this respect at all by men not scientific. The followers of Herbert Spencer, for example, cannot comprehend why scientific men place Darwin so infinitely above Spencer, since the theories of the latter are so much grander and more comprehensive. They cannot understand that it is not the sublimity of Darwin's theories which makes him admired by men of science, but that it is rather his minute, systematic, extensive, and strict scientific researches which have given his theories a more favorable reception--theories which in themselves would barely command scientific respect. And this misunderstanding belongs to all those metaphysicians who fancy themselves men of science on account of their metaphysics. This same scientific spirit has been equally misunderstood as it is found in the schoolmen. They have been above all things found fault with because they do not write a literary style and do not "study in a literary spirit." The men who make this objection can not possibly comprehend the real merits of modern science. If the words quidditas, entitas, and haecceitas, are to excite our disgust, what shall we say of the Latin of the botanists, and the style of any technically scientific work. As for that phrase "studying in a literary spirit" it is impossible to express how nauseating it is to any scientific man, yes even to the scientific linguist. But above all things it is the searching thoroughness of the schoolmen which affiliates them with men of science and separates them, world-wide, from modern so-called philosophers. The thoroughness I allude to consists in this that in adopting any theory, they go about everywhere, they devote their whole energies and lives, in putting it to tests bona fide--not such as shall merely add a new spangle to the glitter of their proofs but such as shall really go towards satisfying their restless insatiable impulse to put their opinions to the test. Having a theory they must apply it to every subject and to every branch of every subject to see whether it produces a result in accordance with the only criteria they were able to apply--the truth of the catholic faith and the teaching of the Prince of Philosophers. Mr. George Henry Lewes in his work on Aristotle seems to me to have come pretty near to stating the true cause of the success of modern science when he has said that it was Verification. I should express it in this way: modern students of science have been successful, because they have spent their lives not in their libraries and museums but in their laboratories and in the field--and while in their laboratories and in the field they have been not gazing on nature with a vacant eye, that is in passive perception unassisted by thought--but have been observing--that is perceiving by the aid of analysis,--and testing suggestions of theories. The cause of their success has been that the motive which has carried them to the laboratory and the field has been a craving to know how things really were and an interest in finding out whether or not general propositions actually held good--which has overbalanced all prejudice, all vanity, and all passion. Now it is plainly not an essential part of this method in general, that the tests were made by the observation of natural objects. For the immense progress which modern mathematics has made is also to be explained by the same intense interest in testing general propositions and particular cases--only the tests were applied by means of particular demonstrations. This is observation, still, for as the great mathematician Gauss has declared--Algebra is a science of the eye,--only it is observation of artificial objects and of a highly recondite character. Now this same unwearied interest in testing general propositions is what produced those long rows of folios of the schoolmen,--and if the test which they employed is of only limited validity so that they could not unhampered go on indefinitely to further discoveries, yet the spirit, which is the most essential thing--the motive, was nearly the same. And how different this spirit is from that of the major part, though not all, of modern philosophers--even of those who have called themselves empirical, no man who is actuated by it can fail to perceive.

One consequence of the dependence of logical thought in the middle ages upon Aristotle is that the state of development of logic at any time may be measured by the amount of Aristotle's writings which were known to the Western world. At the time of the great discussion between the nominalists and realists in the 12th century the only works of Aristotle which were thoroughly known were the Categories and Peri Hermeneias, two small treatises forming less than a sixtieth of his works as we now know them and of course a much smaller proportion of them as they originally existed. There was also some knowledge of the Prior Analytics but not much. Porphyry's introduction to the categories was well known and the authority of it was nearly equal to that of Aristotle. This treatise concerns the logical nature of genus, species, difference, property, and accident; and is a work of great value and interest. A sentence of this book is said by Cousin to have created scholastic philosophy, which is as true as such eminently French statements usually are. It is however correct that it was in great measure the study of this book which resulted in course of time in the discussion concerning nominalism and realism; but to mistake this discussion for all scholastic philosophy argues great ignorance of the subject,--an ignorance excusable when Cousin wrote but not now.

Before we come to this dispute it will be well to give a glance at the state of opinions upon the subject before the dispute began and as these opinions were much influenced by Scotus Erigena, I will say a word or two about this man.

Scotus Erigena was an Irishman who lived in the ninth century,--when Ireland was very far beyond the rest of Western Europe in intellectual culture,--when in fact Ireland alone had any learning,--and was sending missionaries to France, England, and Germany who first roused these countries from utter barbarism. He has excited great interest in our own day and many books have been written about him. Various editions of his different works have been published of which the most important is his De Divisione Naturae. Hauréau has in the 21st volume of the Notices of manuscripts of the French academy published some extracts from a gloss supposed to be by him upon Porphyry. Works upon his Life and Writings of Scotus have been published by Hjort, Staudenmaier, Taillandier, Möller, Christlieb, and Huber. Although he is not chiefly a logician his writings are of great interest for this history of logic and I should gladly devote several lectures to the consideration of them. This pleasure I must deny myself and shall speak of Scotus Erigena not to explain his position but only to throw a light on those who followed after him and were influenced by him. He is usually and rightly reckoned as an extreme realist and yet the extremest nominalists such as Roscellin were regarded as his followers. How could this be?

For one thing we perceive that Erigena attaches a vast importance to words. In consequence of this he seems to suppose that non-existences are as real as existences. He begins his work De divisione naturae by dividing all things into those which are and those which are not. In another place he declares that no philosopher rightly denies that possibles and impossibles are to be reckoned among the number of things. And such expressions are in fact constantly met with in his works. He does not seem to see that as the ancient philosopher said "Being only is and nothing is altogether not." Thus he says that the name Nothing signifies the ineffable, incomprehensible, and inaccessible brightness of the Divine nature which is unknown to every understanding of man or of Angel, which "dum per se ipsam cogitatur" neither is nor was nor will be. And he describes creation as the production out of the negations of things which are and which are not, the affirmations of all things which are and which are not. Again he says "Darkness is not nothing but something; otherwise the Scripture would not say 'and God called the light day and the darkness he called night'." Thus you perceive he has the idea that the immediate immaterial object of a name is something.