The Project Gutenberg eBook ofLogic, Inductive and Deductive

The Project Gutenberg eBook ofLogic, Inductive and DeductiveThis ebook is for the use of anyone anywhere in the United States and most other parts of the world at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this ebook or online atwww.gutenberg.org. If you are not located in the United States, you will have to check the laws of the country where you are located before using this eBook.Title: Logic, Inductive and DeductiveAuthor: William MintoRelease date: March 27, 2010 [eBook #31796]Language: EnglishCredits: Produced by Thierry Alberto, Lesley Halamek and the OnlineDistributed Proofreading Team at http://www.pgdp.net*** START OF THE PROJECT GUTENBERG EBOOK LOGIC, INDUCTIVE AND DEDUCTIVE ***

This ebook is for the use of anyone anywhere in the United States and most other parts of the world at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this ebook or online atwww.gutenberg.org. If you are not located in the United States, you will have to check the laws of the country where you are located before using this eBook.

Title: Logic, Inductive and DeductiveAuthor: William MintoRelease date: March 27, 2010 [eBook #31796]Language: EnglishCredits: Produced by Thierry Alberto, Lesley Halamek and the OnlineDistributed Proofreading Team at http://www.pgdp.net

Title: Logic, Inductive and Deductive

Author: William Minto

Release date: March 27, 2010 [eBook #31796]

Language: English

Credits: Produced by Thierry Alberto, Lesley Halamek and the OnlineDistributed Proofreading Team at http://www.pgdp.net

*** START OF THE PROJECT GUTENBERG EBOOK LOGIC, INDUCTIVE AND DEDUCTIVE ***

Published May, 1893Reprinted December, 1893"November, 1894"January, 1899"August, 1904"June, 1909"September, 1912"July, 1913"January, 1915

HON. LL.D. ST. ANDREWSLate Professor of Logic in the University of Aberdeen

In this little treatise two things are attempted that at first might appear incompatible. One of them is to put the study of logical formulæ on a historical basis. Strangely enough, the scientific evolution of logical forms, is a bit of history that still awaits the zeal and genius of some great scholar. I have neither ambition nor qualification for such amagnum opus, and my life is already more than half spent; but the gap in evolutionary research is so obvious that doubtless some younger man is now at work in the field unknown to me. All that I can hope to do is to act as a humble pioneer according to my imperfect lights. Even the little I have done represents work begun more than twenty years ago, and continuously pursued for the last twelve years during a considerable portion of my time.

The other aim, which might at first appear inconsistent with this, is to increase the power of Logic as a practical discipline. The main purpose of this practical science, or scientific art, is conceived to be the organisation of reason against error, and error in its various kinds is made the basis of the division of the subject. To carry out this practical aim along with the historical one is not hopeless, because throughout itslong history Logic has been a practical science; and, as I have tried to show at some length in introductory chapters, has concerned itself at different periods with the risks of error peculiar to each.

To enumerate the various books, ancient and modern, to which I have been indebted, would be a vain parade. Where I have consciously adopted any distinctive recent contribution to the long line of tradition, I have made particular acknowledgment. My greatest obligation is to my old professor, Alexander Bain, to whom I owe my first interest in the subject, and more details than I can possibly separate from the general body of my knowledge.

W. M.

Aberdeen,January, 1893.

Since these sentences were written, the author of this book has died; and Professor Minto'sLogicis his last contribution to the literature of his country. It embodies a large part of his teaching in the philosophical class-room of his University, and doubtless reflects the spirit of the whole of it.

Scottish Philosophy has lost in him one of its typical representatives, and the University of the North one of its most stimulating teachers. There have been few more distinguished men than William Minto in the professoriate of Aberdeen; and the memory of what he was, of his wide and varied learning, his brilliant conversation, his urbanity, and his rare power of sympathy with men with whose opinions he did not agree, will remain a possession to many who mourn his loss.

It will be something if this little book keeps his memory alive, both amongst the students who owed so much to him, and in the large circle of friends who used to feel the charm of his personality.

WILLIAM KNIGHT.

fancy rule

This Series is primarily designed to aid the University Extension Movement throughout Great Britain and America, and to supply the need so widely felt by students, of Text-books for study and reference, in connexion with the authorised Courses of Lectures.

The Manuals differ from those already in existence in that they are not intended for School use, or for Examination purposes; and that their aim is to educate, rather than to inform. The statement of details is meant to illustrate the working of general laws, and the development of principles; while the historical evolution of the subject dealt with is kept in view, along with its philosophical significance.

The remarkable success which has attended University Extension in Britain has been partly due to the combination of scientific treatment with popularity, and to the union of simplicity with thoroughness. This movement, however, can only reach those resident in the larger centres of population, while all over the country there are thoughtful persons who desire the same kind of teaching. It is for them also that this Series is designed. Its aim is to supply the general reader with the same kind of teaching as is given in the Lectures, and to reflect the spirit which has characterised the movement, viz., the combination of principles with facts, and of methods with results.

The Manuals are also intended to be contributions to the Literature of the Subjects with which they respectively deal, quite apart from University Extension; and some of them will be found to meet a general rather than a special want.

They will be issued simultaneously in England and America. Volumes dealing with separate sections of Literature, Science, Philosophy, History, and Art have been assigned to representative literary men, to University Professors, or to Extension Lecturers connected with Oxford, Cambridge, London, and the Universities of Scotland and Ireland.

A list of the works in this Series will be found at the end of the volume.

The question has sometimes been asked, Where should we begin in Logic? Particularly within the present century has this difficulty been felt, when the study of Logic has been revived and made intricate by the different purposes of its cultivators.

Where did the founder of Logic begin? Where did Aristotle begin? This seems to be the simplest way of settling where we should begin, for the system shaped by Aristotle is still the trunk of the tree, though there have been so many offshoots from the old stump and so many parasitic plants have wound themselves round it that Logic is now almost as tangled a growth as the Yews of Borrowdale—

An intertwisted mass of fibres serpentineUpcoiling and inveterately convolved.

An intertwisted mass of fibres serpentine

Upcoiling and inveterately convolved.

It used to be said that Logic had remained for two thousand years precisely as Aristotle left it. It was an example of a science or art perfected at one stroke by the genius of its first inventor. The bewildered student must often wish that this were so: it is only superficially true. Much of Aristotle's nomenclature and his central formulæ have been retained, but theyhave been very variously supplemented and interpreted to very different purposes—often to no purpose at all.

The Cambridge mathematician's boast about his new theorem—"The best of it all is that it can never by any possibility be made of the slightest use to anybody for anything"—might be made with truth about many of the later developments of Logic. We may say the same, indeed, about the later developments of any subject that has been a playground for generation after generation of acute intellects, happy in their own disinterested exercise. Educational subjects—subjects appropriated for the general schooling of young minds—are particularly apt to be developed out of the lines of their original intention. So many influences conspire to pervert the original aim. The convenience of the teacher, the convenience of the learner, the love of novelty, the love of symmetry, the love of subtlety; easy-going indolence on the one hand and intellectual restlessness on the other—all these motives act from within on traditional matter without regard to any external purpose whatever. Thus in Logic difficulties have been glossed over and simplified for the dull understanding, while acute minds have revelled in variations and new and ingenious manipulations of the old formulæ, and in multiplication and more exact and symmetrical definition of the old distinctions.

To trace the evolution of the forms and theories of Logic under these various influences during its periods of active development is a task more easily conceived than executed, and one far above the ambition of an introductory treatise. But it is well that even he who writes for beginners should recognise that the forms now commonly used have been evolved out of asimpler tradition. Without entering into the details of the process, it is possible to indicate its main stages, and thus furnish a clue out of the modern labyrinthine confusion of purposes.

How did the Aristotelian Logic originate? Its central feature is the syllogistic forms. In what circumstances did Aristotle invent these? For what purpose? What use did he contemplate for them? In rightly understanding this, we shall understand the original scope or province of Logic, and thus be in a position to understand more clearly how it has been modified, contracted, expanded, and supplemented.

Logic has always made high claims as thescientia scientiarum, the science of sciences. The builders of this Tower of Babel are threatened in these latter days with confusion of tongues. We may escape this danger if we can recover the designs of the founder, and of the master-builders who succeeded him.

Aristotle's Logic has been so long before the world in abstract isolation that we can hardly believe that its form was in any way determined by local accident. A horror as of sacrilege is excited by the bare suggestion that the author of this grand and venerable work, one of the most august monuments of transcendent intellect, was in his day and generation only a pre-eminent tutor or schoolmaster, and that his logical writings were designed for the accomplishment of his pupils in a special art in which every intellectually ambitious young Athenian of the period aspired to excel. Yet such is the plain fact, baldly stated. Aristotle's Logic in its primary aim was as practical as a treatise on Navigation, or "Cavendish on Whist". The latter is the more exact of the twocomparisons. It was in effect in its various parts a series of handbooks for a temporarily fashionable intellectual game, a peculiar mode of disputation or dialectic,1the game of Question and Answer, the game so fully illustrated in the Dialogues of Plato, the game identified with the name of Socrates.

We may lay stress, if we like, on the intellectuality of the game, and the high topics on which it was exercised. It was a game that could flourish only among a peculiarly intellectual people; a people less acute would find little sport in it. The Athenians still take a singular delight in disputation. Youcannot visit Athens without being struck by it. You may still see groups formed round two protagonists in the cafés or the squares, or among the ruins of the Acropolis, in a way to remind you of Socrates and his friends. They do not argue as Gil Blas and his Hibernians did with heat and temper, ending in blows. They argue for the pure love of arguing, the audience sitting or standing by to see fair play with the keenest enjoyment of intellectual thrust and parry. No other people could argue like the Greeks without coming to blows. It is one of their characteristics now, and so it was in old times two thousand years ago. And about a century before Aristotle reached manhood, they had invented this peculiarly difficult and trying species of disputative pastime, in which we find the genesis of Aristotle's logical treatises.

To get a proper idea of this debate by Question and Answer, which we may call Socratic disputation after its most renowned master, one must read some of the dialogues of Plato. I will indicate merely the skeleton of the game, to show how happily it lent itself to Aristotle's analysis of arguments and propositions.

A thesis or proposition is put up for debate,e.g., that knowledge is nothing else than sensible perception,2that it is a greater evil to do wrong than to suffer wrong,3that the love of gain is not reprehensible.4There are two disputants, but they do not speak on the question by turns, so many minutes being allowed to each as in a modern encounter of wits. One of the two, who may be called the Questioner, is limited to askingquestions, the other, the Respondent, is limited to answering. Further, the Respondent can answer only "Yes" or "No," with perhaps a little explanation: on his side the Questioner must ask only questions that admit of the simple answer "Yes" or "No". The Questioner's business is to extract from the Respondent admissions involving the opposite of what he has undertaken to maintain. The Questioner tries in short to make him contradict himself. Only a very stupid Respondent would do this at once: the Questioner plies him with general principles, analogies, plain cases; leads him on from admission to admission, and then putting the admissions together convicts him out of his own mouth of inconsistency.5

Now mark precisely where Aristotle struck in with his invention of the Syllogism, the invention on which he prided himself as specially his own, and the forms of which have clung to Logic ever since, even in the usage of those who deride Aristotle's Moods and Figures as antiquated superstitions. Suppose yourself the Questioner, where did he profess to help you with his mechanism? In effect, as the word Syllogism indicates, it was when you had obtained a number of admissions,and wished to reason them together, to demonstrate how they bore upon the thesis in dispute, how they hung together, how they necessarily involved what you were contending for. And the essence of his mechanism was the reduction of the admitted propositions to common terms, and to certain types or forms which are manifestly equivalent or inter-dependent. Aristotle advised his pupils also in the tactics of the game, but his grand invention was the form or type of admissions that you should strive to obtain, and the effective manipulation of them when you had got them.

An example will show the nature of this help, and what it was worth. To bring the thing nearer home, let us, instead of an example from Plato, whose topics often seem artificial to us now, take a thesis from last century, a paradox still arguable, Mandeville's famous—some would say infamous—paradox that Private Vices are Public Benefits. Undertake to maintain this, and you will have no difficulty in getting a respondent prepared to maintain the negative. The plain men, such as Socrates cross-questioned, would have declared at once that a vice is a vice, and can never do any good to anybody. Your Respondent denies your proposition simply: he upholds that private vices never are public benefits, and defies you to extract from him any admission inconsistent with this. Your task then is to lure him somehow into admitting that in some cases what is vicious in the individual may be of service to the State. This is enough: you are not concerned to establish that this holds of all private vices. A single instance to the contrary is enough to break down his universal negative. You cannot, of course, expect him to make the necessary admission in direct terms:you must go round about. You know, perhaps, that he has confidence in Bishop Butler as a moralist. You try him with the saying: "To aim at public and private good are so far from being inconsistent that they mutually promote each other". Does he admit this?

Perhaps he wants some little explanation or exemplification to enable him to grasp your meaning. This was within the rules of the game. You put cases to him, asking for his "Yes" or "No" to each. Suppose a man goes into Parliament, not out of any zeal for the public good, but in pure vainglory, or to serve his private ends, is it possible for him to render the State good service? Or suppose a milk-seller takes great pains to keep his milk pure, not because he cares for the public health, but because it pays, is this a benefit to the public?

Let these questions be answered in the affirmative, putting you in possession of the admission that some actions undertaken for private ends are of public advantage, what must you extract besides to make good your position as against the Respondent? To see clearly at this stage what now is required, though you have to reach it circuitously, masking your approach under difference of language, would clearly be an advantage. This was the advantage that Aristotle's method offered to supply. A disputant familiar with his analysis would foresee at once that if he could get the Respondent to admit that all actions undertaken for private ends are vicious, the victory was his, while nothing short of this would serve.

Here my reader may interject that he could have seen this without any help from Aristotle, and that anybody may see it without knowing that what he hasto do is, in Aristotelian language, to construct a syllogism in Bokardo. I pass this over. I am not concerned at this point to defend the utility of Aristotle's method. All that I want is to illustrate the kind of use that it was intended for. Perhaps if Aristotle had not habituated men's minds to his analysis, we should none of us have been able to discern coherence and detect incoherence as quickly and clearly as we do now.

But to return to our example. As Aristotle's pupil, you would have seen at the stage we are speaking of that the establishment of your thesis must turn upon the definition of virtue and vice. You must proceed, therefore, to cross-examine your Respondent about this. You are not allowed to ask him what he means by virtue, or what he means by vice. In accordance with the rules of the dialectic, it is your business to propound definitions, and demand his Yes or No to them. You ask him, say, whether he agrees with Shaftesbury's definition of a virtuous action as an action undertaken purely for the good of others. If he assents, it follows that an action undertaken with any suspicion of a self-interested motive cannot be numbered among the virtues. If he agrees, further, that every action must be either vicious or virtuous, you have admissions sufficient to prove your original thesis. All that you have now to do to make your triumph manifest, is to display the admissions you have obtained in common terms.

Some actions done with a self-interested motive are public benefits.All actions done with a self-interested motive are private vices.

Some actions done with a self-interested motive are public benefits.

All actions done with a self-interested motive are private vices.

From these premisses it follows irresistibly that

Some private vices are public benefits.

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