Logic

Preface

When Scholastic Philosophy ceased to be the subject of systematic study in Protestant Univer¬ sities, and was regarded as possessing an historical rather than a scientific interest, there was one branch of it that was treated with less dishonour than the rest. Iti Et-hies and Metaphysics, in Psychology and Natural Theology^ the principles handed down by a tradition unbroken '5Tor cen¬ turies came to be looked upon as antique curiositiesj^or as merely, illustrating the development of human progtess Sand . huinanj thdugij^// -^'bese sciences were either set aside as' things of the past, consisting of fine : spun ..subtleties of no practical value, or else they were reconstructed on an entirely new basis. But with Logic it was different. Its underlying principles and its received method were not so closely and obviously interlaced with the discarded system of theology. It admitted

PREFACE.

rib of bring more easily brought into apparent harmony with the doctrines of the Reformation, because it had not the same direct bearing on Catholic dogma. It was, moreover, far less formidable to the ordinary student. Those who had no stomach for the Science of Being, were nevertheless quite able to acquire a certain moderate acquaintance with the Science and the Laws of Thought. Men chopped Logic harmlessly, and the Logic they chopped was the traditional Logic of the School¬ men, with some slight modifications. The text-book of Dean Aldrich, which has not yet disappeared from Oxford, is mediaeval in its phraseology and its method ; mediaeval, too, in its principles, except where an occasional inconsistency has crept in unawares from the new learning. It still talks of “ second intentions,” and assumes the existence of an Infima Species, and has throughout the wholesome flavour of the moderate realism of sound philosophy.

But this state of things could not last. Sir W. Hamilton, the champion of conceptualism, put forth in his Lectures on Logic a theory of intellectual apprehension quite inconsistent with the traditional doctrine which still lingered in the meagre and obscure phraseology of Dean Aldrich. Sir W. Hamilton's disciple, Dean Mansel, who

PREFACE.

I* carried on the work of philosophic scepticism which his master had inaugurated, published an edition of Aldrich, with explanatory notes and appendices, which pointed out his supposed errors, while John Stuart Mill, with far more ability and a wider grasp than either of the two just named, substi¬ tuted for the halting conceptualism of Hamilton a nominalism which had but a thin veil of plausible fallacies to hide from mankind the utter scepticism which lay beneath it.

Since then, the Kantian principle of antinomies which underlies the Logic of Mansel and Hamilton has boldly come to the front in England under the shadow of the great name of Hegel, and English logicians have either ranged themselves under the banner of one or other of these new schools, or else have sought to cover the glaring inconsistencies of some one of them with patches borrowed from the others, until the modern student has a bewildering choice among a series of guides, each of whom follows a path of his own, leading in the end to obscurity and confusion and self-contradiction, but who are all united in this, that they discard and misrepresent the traditional teaching of Aristotle and of the mediaeval logicians. Their facility in so doing is partly owing to the fact that Aristotle has no methodical treatise cover*

PREFACE.

ing the ground of modern Logic, and St. Thomas gives merely a rapid sketch of the technical part of it in one of his Opuscula. But from the pages of the great philosopher of Pagan times and of the Angelic Doctor of the middle ages, can be gathered by the careful student all the principles necessary for the modern logician. Every Catholic teacher of Logic follows of necessity closely in their steps, and finds in them the solution of every diffi¬ culty, and the treatment — at least the incidental treatment — of almost every question that Logic can propose.

The modern school of Logic departs from the ancient from the very first, as the reader will see as he studies the following pages. The very foun¬ dations are different. The Principle of Contradic¬ tion is in the Hamiltonian system subordinated to that of Identity, while Stuart Mill goes still further astray, and the Hegelians set it altogether aside. The account given by these various schools of the process of intellectual apprehension by which the idea or general notion is arrived at, is one which leads to an utter scepticism. The Doctrine of the relativity of human knowledge is no less at variance with all positive truth, while the modern theory of LJniversals attempts to establish itself on the ruins of the Scholastic Realism by a gross misrepre-

PREFACE.

XI scntation of what Scholastic Realism really means.

It is the object of the present Manual of Logic to lead back the English student into the safe paths of the ancient wisdom, to point out where it is that the speculations of modern philosophizers have quitted the well-trodden high road of truth, and to at least indicate the precipices of incon¬ sistency and self-contradiction to which they conduct the unhappy learner who allows himself to be guided by them. It is, however, impossible, in a compendious text-book like this, to discuss at length the various ramifications of the errors through which the different schools of to-day have gone utterly astray. It has therefore been the aim of the writer to select for attack, as far as possible, the central and distinctive error of each, or the one most likely to throw dust in the eyes of the incautious reader from the very beginning.

This, however, is not the primary object aimed at. The need of a Catholic text-book of Logic in English, corresponding to those which are in general use in Protestant schools and Universities, has been long felt on both sides of the Atlantic. To the more advanced students of our Catholic Colleges a thorough grounding in Logic is a most important clement in their intellectual cultivation. Yet there ili

PREFACE.

has been hitherto no text-book which could be put into their hands for the purposes of private study. The Latin treatises which form the basis of the lectures attended by the young ecclesiastic are quite unsuited for them, apart from the mere difficulties of the language. Their strange phrase¬ ology, the technicalities of their style, the cut and dried method they pursue in their advance from principles to conclusions, their complete severance from modern habits of thought and speech, render them unintelligible to ordinary students without an elaborate explanation on the part of the teacher. He has to cover the dry bones with flesh, to enlarge, illustrate, translate, and simplify, and often entirely reconstruct, before he can reach the average intelligence or rouse any interest in his pupils.

The English text-books hitherto issued have been little more than a literal translation from the Latin, and though they have done a good work in furnishing students unversed in Latin with text¬ books in their own language, yet they have not attempted the further task of translating scholastic into nineteenth-century phraseology. It is hoped that the present Manual may put before our Catholic youth this most important branch of study in a more simple and attractive form. The scholastic

*!!1

terms have not been discarded, but they have been carefully explained and rendered into words which will convey to the man of average edu¬ cation their real meaning. While the scholastic system has been closely adhered to throughout, the dress in which it is clothed is modern, and no previous knowledge is necessary for the young Catholic in whose hands it is placed.

There is another class to whom it is hoped that the present text-book may prove useful. Many a Protestant student, perplexed and bewildered by the rival claims of half a dozen different systems, each at variance with the rest, and often also at variance with itself as well, is inclined to give up the search for truth in despair and to fall back on the Hamiltonian doctrine of the Relativity of Knowledge, or in other words, on the non-existence of truth at all. Such a one often craves in his heart after some leader on whom he can rely, some one who represents, not the newly-fangled inven¬ tions of the individual, but the traditional authority of centuries. He would fain know whether amid Catholic philosophers there is the same discord and the same contradiction as among Protestants, and would eagerly drink in the teaching of one who speaks, not in his own name or that of some modern thcorizer, but in the name of the men of

PREFACE.

tit

genius, who gave themselves to the study of Logic Irom the days of Aristotle till the unhappy period when the old learning was discarded with con¬ tempt by the ignorance of the Reformers. To any such inquirer this text-book offers the ordinary Catholic teaching grounded on Aristotle and set forth by St. Thomas of Aquin, which flourishes as vigorously as ever in every centre of higher Catholic education. If there is any departure from the doctrines of St. Thomas in these pages, it is there without the knowledge of their writer, whose object it has been to follow throughout in the footsteps of the Angelic Doctor.

There is another class to whom such a text-book as this will be a real boon, to whose existence the writer can testify from personal experience. Con¬ verts to the Catholic Church, trained in the English Colleges and Universities, have unconsciously drunk in a number of principles, some true, some false, from their earliest years, and are often not a little puzzled to discern the true from the false. Perhaps in their early days Hamilton and Jevons, Mansel or Veitch, had represented to them the orthodox school, and Mill and Spencer and Hegel a more consistent and at the same time more sceptical system. On submission to the Church, they would fain know how far these rival claimants possess any

PREFACE.

if fragments, large or small, of solid truth, and where they each and all wander away into error. In the following pages this need has been kept in view, and the Author has sought to write what would have been useful to himself twenty years ago, when he made unsuccessful endeavours to master by private study the principles of Catholic philosophy from inscrutable Latin text-books.

Last of all we must remember that in these days the old ideas respecting the limits of feminine education have been not a little modified. This is not the place to discuss the advantages and disadvantages of a more enlarged intellectual train¬ ing for women. It is enough to say that the change which is being introduced is in many respects only a re-assertion of what was common enough in Catholic times. It is an undoubted gain to the cause of Truth that women of cultivated tastes should be trained to think correctly, and should have such a knowledge of the principles of Logic as may help them thereto. In Convent schools and other Catholic institutions the higher education is steadily making way, especially in the United States, and the study of Logic is an im¬ portant element in it. The present volume is one which, even if it is not put into the hands of the younger students, is well suited for the

PREFACE.

:vi

Teacher’s use in the instruction of her Catholic pupils, as well as for those whose general training may give them an interest in the subject and a desire to investigate it for themselves.

One word to those who may desire to know the best order in which to study the various parts of Catholic Philosophy. Although this Text-book of Logic has not been the first to appear in order of time, it is the one which naturally comes first in order of thought, and the Student is recommended to pass from it to the Text-book of I'irst Principles, and so on to Ethics, Natural Theology, Psychology, and the difficult though important subject of General Metaphysics*

Introduction

PAGE

Chapter I. — The Province of Logic • • 1 ,, II —The Definition ok Logic . • • x5

„ Ill. — The Foundations of Logic . . • 29

I. The Principle of Contradiction . • 33

II. The Principle of Identity . . • 42

, IV.— The Foundations of Logic {continued) . 5°

„ V.— The Foundations of Logic ( continued ) . 71

III. The Principle of Causation . • 72

IV. The Principle of Excluded Middle . . 79

M VI.— The Three Operations of Thought . 92

Part I.— Of Simple Apprehension Or Conception

„ VII. — Simple Apprehension {continued). Modern

Errors respecting it 121

„ VIII. — The Doctrine of Universals . . 14°

M IX.— The Heads of Predicabi.es . . • 163

,, X.— Definition . . • J93

XI.— Division 225

CONTENTS.

xvih

Part Ii.— Of Judgment Or Assent. Pagb

Chapter 1 — Judgment ..... 245

Divisions of Judgment .... 250 r II —Propositions, their Nature and Divisions 261 Divisions of Propositions .... 266 ,, III. -Import of Propositions. Various kinds of

Propositions . . . . . 280

„ IV.— -The Opposition and Conversion of Pro¬ positions ..... 293

PART III.— OF REASONING OR ARGUMENT. Chapter I. — Reasoning ..... 305

„ II. — The Syllogism and its Laws . . 313

Canons of the Syllogism . . -315

Dictum de omni et nullo . . . 316

General Rules of the Syllogism . . 316

H III. — The Figures of the Syllogism. Reduction 324 Rules of the First Figure . . . 332

Rules of the Second Figure . . . 333

Rules of the Third Figure . . . 334

Rules of the Fourth I'igure . . . 335

Reduction ..... 339

„ IV.— Various kinds of Syllogisms . . 34S

Other Variations of the Syllogism . . 359

M VI. — Material induction . . . 376

Method of Agreement .... 389

Method of Difference .... 390

Method of Concomitant Variations . . 393

Method of Residues , 395

CONTENTS. xix

PAGE

Chapter VII.— Example and Analogy . .402

Example • 402

VIII — The Matter of the Syllogism . • 412

I. Demonstrative Syllogisms . . .419

II. Probable Syllogisms . . .424

„ IX.— Fallacies • • • 432

I. Fallacies of Language . . -434

II. Fallacies outside Language . . .445

X- _ Method and its Laws . , . 461

appendix.

LOGIC.

Pari I.

CHAPTER I.

THE PROVINCE OF LOGIC.

Importance of Logic — Aim of Logic — Meaning of the word — Logic and Grammar — Logic in its relation to Thought — Different meanings of Thought — Logic and Psychology — Logic and Meta¬ physics — Formal and Material Logic, and their respective provinces — Formal Logic necessary to Material — Meaning of Formal Logic — The Laws of Thought — Logic in its relation to the Laws of Thought.

The importance of the study of Logic is derived from its undeniable claim to an universal dominion over the minds of men. No one can ever think correctly unless he thinks logically. No one can judge aright unless his judgment is one which Logic can approve. No one can arrive at well-grounded conclusions unless he argues in conformity with the laws of Logic. He who professes a system of Philosophy, or Theology, or Science which is in any respect opposed to logical principles, thereby declares his system to be false and irrational, and himself an intellectual impostor. Logic must of necessity control with its unerring laws every pro¬ cess of thought, every act of judgment, every chain b

THE PROVINCE OF LOGIC.

of argument ; else the process of thought is faulty, the act of judgment unwarrantable, the chain ol argument incorrect.

The ultimate end aimed at in the study of Logic is to train the human mind to exactness of thought. It is not to make a man ready in argument, nor to add to the stock of human knowledge, but to teach us to think correctly. As in a liberal education the end aimed at is not to impart to the student a vast number of accumulated facts, but to stimulate the desire for acquiring information for himself, to furnish him with the means of doing so, and to enable him to make a good use of the information when acquired, so the ultimate object of the study of Logic is not so much to supply us with a detailed analysis of our processes of thought, as to ensure their correct performance. This is the end it has in view in laying down the Laws of Thought which are its foundation, and in analyzing the various operations which fall within its province. This it aims at still more directly in pointing out the mani¬ fold dangers to which thinking is exposed, and the fallacies by which the thinker is most liable to be deceived. It seeks to arm the logical student cap-a-pie, so that he may be able to detect at a glance the incorrect judgment or unwarranted assumption. It gives him the clue to the carefully concealed fallacy, and enables him to expose its weakness, to show where the inference is faulty, or where the terms are used in an ambiguous sense, or where statements are put forward as identical when they are really different from each other.

MEANING OF THE WORD.

But what is Logic ? Before we consider this question, we will look at the origin of the word, as an useful guide to its true meaning.

Logic is derived from the Greek Logos, which has the double meaning of word and thought . It is used in classic authors indiscriminately for the internal word present in the mind, and the external word uttered by the lips. It has, therefore, no exact equivalent in English, although in theological lan¬ guage word is sometimes used for that which is hidden in the intellect without finding external expression.1 But such usage is exceptional, and in ordinary English word implies some form of spoken language.

The double use of the Greek word Logos corre¬ sponds to the double nature of the subject-matter of Logic. As Logos is primarily the internal thought, and secondarily the external expression of the thought, so Logic is primarily concerned with thought, secondarily with language, as expressing thought. The connection between correct thought and correct language is so intimate, that any branch of knowledge which treats of the one must to some extent include the other. Logic, therefore, as being concerned with thought, is necessarily concerned also with language. Here we see its relation to Grammar. Both Logic and Grammar have to do

1 Thus The Word is used to express the Second Person of the Blessed Trinity, the Eternal Wisdom of God, hidden in the Intellect of the Eternal Father before all ages (“ The Word was made Flesh ”), and also the interior voice speaking with Divine authority to the mind of the prophets (“ The word of the Lord came to Jonas,’’ &c.).

THE PROVINCE OF LOGIC.

with thought and language, but Logic has to do with thought primarily and essentially, and with language secondarily, and only so far as it affects thought, whereas Grammar, on the other hand, treats of language primarily and essentially, and of thought only secondarily, and so far as is necessary for the due treatment of language.

Logic then is a branch of knowledge concerned with Thought. But this is not sufficient for our Definition. What do we mean by Thought ? Has Logic to do with all our thoughts ? Does it include an investigation into the origin of Thought, the subject-matter of Thought, the various mental pro¬ cesses which are connected with Thought ? Does it treat of Thought in general, or is it limited to some special province or department of Thought ?

In order to have an accurate knowledge of the province of Logic, we must first of all have an accurate knowledge of Thought. Thought is used in two different senses.

r. It is sometimes used to include every mental process, every activity of those faculties which belong to the sphere of intelligent (as distinguished from intellectual) life. Thus I say that my friend in Australia is in my thoughts , and by this I mean that he is present in my memory, and his image dwells in my imaginative faculty. A child is said to be thinking of its dinner, when we see it restless and fidgetty in the school-room as the time of its mid¬ day meal approaches, and we mean thereby that a vague, half-conscious recollection of the expected food, and a desire to partake of it, is present to its

Logic in its relation to thought. a mind. In this sense animals may be said to thuik. The dog thinks of the rat when his master makes a scratching noise in the corner of the room ; he thinks of the pain of some recent castigation when he sees the whip. Thinking , in this meaning of the word, belongs to the material faculties of memory and imagination, as well as to the immaterial faculty of intellect.1

2. Thought is also used in the narrower and stricter sense of the exercise of our intellectual faculties properly so called, of that immaterial faculty which brings within the range of our know¬ ledge things above and beyond sense, which recog¬ nizes in things sensible that which is suprasensible, and contemplates under the external appearance the underlying nature. It is the recognition in things around of that which makes them to be what they are, of the inner reality hidden under the shell of the external and material object of sense, of that which in scholastic language is termed the essence, or quiddity, because it answers the question,2 3 What is this ? Quid est hoc ? Thought is the grasping ol that common nature which is the foundation of all classification, and binds together existing things

1 When thought is used in this sense, it is true that in the case of rational beings there is a real intellectual apprehension, since this necessarily accompanies every act of their imagination. But it is the sensitive act of which we are speaking when we use in reference to such acts the word think, since we employ it in the same sense of

the acts of men and of the lower animals.

3 Quidditas is the somewhat barbarous but very expressive equivalent of the Aristotelian phrase, to rl hv tlvai. The essence or quiddity of a thing consists in its corresponding to the pattern

THE PROVINCE OF LOGIC.

into what we call classes, or kinds, or species. It is the apprehension of things immaterial and spiritual, and of things material only after its own immaterial fashion.

But it is more than this. It also includes those processes by which the intellect compares together the ideas which it has framed for itself from objects about and around us, pronounces on their agreement or disagreement, declares them to be compatible or incompatible, identical or different from each other. The decisions thus arrived at it places side by side, and from them passes to further propositions deducible from them, comparing these together in their turn, and thus constructing arguments and chains of argument with an activity of which the only limit is the finite character of Thought. In other words, Thought apprehends, judges, reasons, not about individual objects, apprehended directly and immediately as individuals, not about sensible things in their capacity of objects of sense, but about the inner nature which underlies all things, whether sensible or suprasensible, material or spiritual, and which intellect alone can grasp and make its own.

Animals therefore are incapable of Thought in this higher sense. Their knowledge is limited to things sensible and material, and that which is essentially dependent on sense and matter. They have no capacity for apprehending the inner nature

after which it was fashioned. Hence rf ^F-what is its nature? what was it intended to be by its Creator ? And therefore ri r» ijr •Jycu ~ the being what it was intended to be by its Creator.

of things. Animals can form a sort of judgment, it ia true, about things of sense, and act in consequence of sensible impressions, as if they drew a conclusion from such judgments, in a way that often strangely counterfeits, intellectual activity, but they never get beyond the region of sense, and exercise their facul¬ ties on objects which admit of being painted on the Imagination, not on those which belong to the special province of Intellect.

But is Logic concerned with all that concerns Thought? with the processes, for instance, by which materials are supplied to the intellect for it to think about ? or with the various phenomena of Thought that observation and experience reveal to us ? Is it concerned with the reliance to be placed on our thoughts, and their correspondence with the things about which we think ? Does an investigation into the various faculties of the mind that think, and of their mutual relation to each other, lie within the scope of Logic ? While we contend for all reasonable liberty in defining the domain of Logic, we must be careful not to encroach on kindred sciences.

Logic is not concerned with an analysis of our thinking faculties. This belongs to Psychology, or the science of life, of intellectual life, as well as oi its lower manifestations. To Psychology, moreover, belongs the study of the various phenomena oi thought, of the facts of intellect that we gain by observation. To Psychology belongs the analysis of the processes previous to Thought, by which materials are furnished to the Intellect. To Psy-

I

THE PROVINCE OF LOGIC.

chology belongs the determination of the exact distinction between the sensitive and the non-sensi¬ tive faculties of the mind, and of their mutual dependence on each other, and though the two sciences have a certain amount of common ground, yet we may say in general that Psychology is con¬ cerned with all the operations of mind in its widest sense, while Logic is concerned only with those which contribute to correct thinking.

Nor is Logic concerned with the objects about which we think, except in so far as they are repre¬ sented in the thinking mind. Regarded in them¬ selves they fall under the domain of Metaphysics, which investigates the inner nature of things, and regards them as in themselves they are. The science of Metaphysics determines the nature of various forms of being , of essence and substance, of cause and effect, of goodness, unity, and truth. It treats of that which lies outside the mind, and contemplates it in its objective reality. Logic, on the other hand, treats of that which is within the mind only, and contemplates it in so far as it is a part of the intellectual furniture.

But is it within the province of Logic to decide on the reliance to be placed on our thoughts, or their trustworthiness as representations of the internal objects about which we think? Here we come on an important distinction between the two parts of Logic.

i. Formal Logic has a limited, though a most important province. Its jurisdiction is confined to those thoughts which already exist within the mind

FORMAL AND MATERIAL LOGIC.

and have passed the barrier between intellect and sense. It has to take for granted that the processes by which they have been received were correctly performed. It accepts such thoughts as the materials it has to employ, it pronounces on their character as thus received, on their various rela¬ tions to each other, whether of inclusion or exclu¬ sion, compatibility or incompatibility, and from the decisions passed it passes on to other decisions, compares one with another and pronounces some fresh decision as the result of the comparison. It discusses the ideas which are the objects of thought, and the judgments which express their mutual relation, and the arguments which result from com¬ bined judgments. Furthermore, as ideas, judgments, arguments, must all be expressed in words, it treats of terms as expressing ideas, propositions as expres¬ sing judgments, syllogisms as expressing arguments.

2. Material or Applied Logic includes a much wider province. It is not satisfied with taking . its materials for granted, but examines into the processes by which those materials are brought into the mind, so far as is necessary to their being correctly performed. It includes the consideration of the correspondence of the object of thought as it exists in itself and as it exists in the thinking mind. It pronounces on the nature of evidence, on the various degrees of certitude from absolute ignorance to the highest possible assurance of truth : on the various grounds of certitude : on the distinctions of doubt, opinion, knowledge, faith, on the necessity ol some kind of certitude if we are to think at all, and

THE PROVINCE OF LOGIC.

io of the consequent folly of universal scepticism. It acts the part of critic and investigator of truth, and its investigations carry it outside the limits of the thinking process properly so called, in order that it may defend this process against the dangers to which it is exposed from without.

In the present volume we shall confine ourselves, though not with the rigour of too close an exactitude, to Formal Logic. Material Logic is rather a part of Fundamental Philosophy, and would lead us too far afield. Yet we shall find it necessary to speak of certain processes which strictly speaking lie outside Formal Logic on account of the confusion that has been introduced by the speculations of various modern authors, who make it necessary for us fromtime to time to make excursions outside our own proper province in order to keep its limits intact, and beat our opponents back when they seek to bring confusion into the realm of Logic Pure.