Elements of logick

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Preface

TO THE FIRST EDITION.

Most of the treatises of Logick in common use have been formed on the model of the ancient systems, and are encumbered with many scholastick subtilties and unimportant distinctions. The instructions, which they furnish on the subject of ratiocination, consist of very little more than a description of the syllogism, and a few general principles of demonstrative reasoning. They contain no elements nor rules to assist us in reasoning on subjects of probability, or on the ordinary events of human life. The manner, in which these books are written, is ill adapted to the comprehension of young minds. In explaining the operations of reasoning, many technical terms and arbitrary forms are employed, of which the tendency is rather to embarrass and perplex, than to instruct the learner.

Though much has been written, of late years, on the powers and operations of the mind, yet there have been but few attempts to form a system of Logick for the use of those, who are commencing the study. Collard has improved the syllogism, by simplifying its principles, and divesting it of its ancient trappings of modes and figures. Condillac has proved the importance of the method of induction, by pointing out the manner, in

IV PREFACE.

which Nature teaches us to analyze the objects, which she presents to our observation. In " An Essay on the Elements, Principles, and different Modes of Reasoning," by Richard Kirwan, LL. D. all the subjects, which properly fall within the precincts of Logick, are amply discussed. But this work is too minute and prolix to be used as a text book in seminaries of education. Every person, who is much conversant with this department of knowledge, must have perceived the want of a treatise of Logick, more elementary, and better accommodated to the present improved state of the philosophy of the mind, than any cf those, which are now in use.

The professed object of Logick is to furnish rules for the direction of the understanding in its various inquiries after knowledge. It should, therefore, teach the principles of every species of reasoning, which we have occasion to make use of, both in the pursuits of science, and in the ordinary transactions of life. Demonstrative reasoning can be employed only about general truths, and such relations as are in their nature immutable. It is of little use in regulating our judgments and conclusions concerning events, which are irregular in their occurrence, and which depend on contingent circumstances. To reason on subjects of this kind, it is necessary to understand the nature of ruoral evidence, and the grounds of probability. It is by moral evidence alone, that we reason on historical facts, and the casual occurrences of life. It is also this evidence, which influences our conclusions on the important and interesting subjects of government, morals, and religion.

PREFACE. V

Under these impressions, the writer of this compend has pursued the following plan. After passing through the customary distinctions of terms and propositions, he has given a brief account of moral evidence, and pointed out the circumstances, which distinguish it from demonstrative. A concise view is then given of the different forms of reasoning, with the principles, on which they respectively proceed.

The books, which have been principally consulted in forming this summary, and in which the greatest part of the following principles may be found, are Watts' Logick, Locke's Essay on the Understanding, Reid's Essays on the Intellectual Powers, Stewart's Elements of the Philosophy of the Mind, Beattie's Essay on Truth, Tatham's Chart and Scale of Truth, Collard's Essentials of Logick, Kirwan's Logick, Campbell's Philosophy of Rhetorick, Gambier's Introduction to Moral Evidence, Belsham's Compendium of Logick, and Scott's Elements of Intellectual Philosophy.

Where passages have been borrowed entire, credit is given in the usual way. At the close of the several chapters may be found the names of those authors, from whom particular assistance has been derived. 1*

PREFACE

TO THE THIRD EDITION,

The present edition of the Elements of Logick is printed in a smaller type than either of the preceding, in order that the copies may be afforded at a reduced price. The author has carefully revised the work, and has enlarged it by the addition of a few pages, containing some general principles and rules respecting controversy, and also a system of rules for the interpretation of written documents. These have been collected with care from authors of high reputation, and, it is hoped, will not be thought an unsuitable appendage to a system of logick. In a few places, slight alterations have been made in the language and in the arrangement ; and some notes have been inserted at the end of the book, which were not in the preceding editions.

Harvard College, Nov. 1821

Introduction

1. The purpose of Logick is to direct the intellectual powers in the investigation of truths and in the communication of it to others. Its foundation is laid in the philosophy of the human mind, inasmuch as it explains many of its powers and operations, and traces the progress of knowledge, from the first and most simple perceptions of outward objects, to those remoter truths and discoveries, which result from the operations of reasoning.

2. Logick instructs us in the right use of terms, and distinguishes their various kinds. It teaches the nature and varieties of propositions ; explains their properties, modifica-

14 INTRODUCTION.

tions, and essential parts. It analyzes the structure of arguments, and shows how their truth may be discovered, or their fallacy detected. Lastly, it describes those methods of classification and arrangement, which will best enable us to retain and apply the knowledge, which we have acquired.

3. Though the understanding would be incapable of any high degree of improvement, without the aid of rules and principles, yet these are insufficient without practice and experience. The powers of the mind, like those of the body, must be strengthened by use. The art of reasoning skilfully can be acquired only by a long and careful exercise of the reasoning faculty, on different subjects and in various ways. The rules of logick afford assistance to this faculty, not less important than that, which our animal strength derives from the aid of mechanical powers and engines. They guide its operations, and supply it with suitable instruments for overcoming the difficulties, by which it would be impeded in its search after truth.

4. In the following compend, the subjects of logick are distributed into three parts. The first contains a brief description of the leading powers and operations of the mind : The second, of the several kinds of terms and propositions. The third comprises an explanation of moral and demonstrative evidence ; of the different modes of reasoning ; of sophisms ; and of method, or disposition.

Chapter First. , Perception And Consciousness

5. Perception is the first state or afFecticn of the human mind. By this we gain all om knowledge of the powers and qualities of the material objects about us. The instruments of perception are the five corporeal senses, seeing, feeling, hearing, tasting, end smelling. All the intercourse, which the mind has with the material world, is carried on by these organs. Of the manner, in which this intercourse proceeds, we have no knowledge. From experience we learn, that a sensible alteration takes place in the mind, whenever any outward object is so situated, as to affect either of the senses. The change, produced in the mind by the impression of the object on the organ of sense, is denominated sensation.

The word perception denotes the knowledge, that we gain by sensation, of some quality in the object ;* which knowledge may be retained by the mind after the object is removed, and it is then usually called an idea or notion. The external object, or quality perceived, is denominated the object of perception, or the archetype of the idea.

6. If either of the senses be wholly wanting, the mind must be forever destitute of all that class of ideas, which it is the office of that sense to furnish. If either be possessed but imperfectly, the ideas, received from it, are liable to be faint and indistinct. But the usual effects of dull organs may be in a great measure obviated, by an increased effort of attention, while the objects are present ; as is manifest in the case of persons, who have had their hearing in some degree impaired.

It is from habitual inattention to our sensations, more than from dulness in the organs

* " The sensations, which are excited in the mind by external M objects, and the perceptions of material qualities, which follow " those sensations, are to be distinguished from each other only " by long habits of patient reflection." Stewart, Elem. vol i. ch. v. part 2d, sect. 1st.

of sense, that so few of the objects, which strike our senses, leave any durable traces in the mind ; and that those notions, which do remain, are so often obscure and indistinct. As the perceptions of sense are the first elements of our knowledge, we should cultivate the habit of carefully noticing the things, which we see, feel, and the like ; in order that the notions, which we form of them, may be clear and distinct.

7. Consciousness, or reflection, is that notice, which the mind takes of its own operations, and modes of existence,* By this we are made acquainted with the successive changes, which take place in the state of our minds. Consciousness is similar to perception, though the qualities of body, which are the objects of the latter, bear no resemblance to the thoughts and operations of the mind, which are the objects of the former. The mind, at least whilst we are awake, is constantly employed in some mode of thinking, or in some exertion of its powers ; and all the operations, passions, and affections of the mind, are necessarily subject to its own observation. Thus, by

* See note A, at the end of the book.

2* consciousness, we learn what is expressed by the words compare, reason, doubt, assent, joy, in the same manner as, by perception, we gain a knowledge of sweet, green, soft, cold.

8. Both perception and consciousness, considered apart from any acts of attention, accompanying them, are involuntary states of mind. We are often active in bringing external objects within our view, and in varying their position, for the purpose of careful observation ; so, by a voluntary effort, we excite operations, and cause changes in the mind ; but the knowledge, that we gain in each case, of the subjects thus presented, is without any act of the will. We cannot avoid hearing many sounds, and seeing the objects, which are placed before our eyes. We are constrained to smell odours, taste our food, and feel bodies, when in contact with our own. It is the same with respect to the operations and states of the mind. We are unable to compare, reason, abstract; to feel pain, pleasure, disgust, or the like, without being conscious of those states.

ATTENTION. 19

Chapter Second. Attention

9. Attention expresses the immediate direction of the mind to a subject. The distinctness of our notions, the correctness of our judgments, and the improvement of all our intellectual powers, depend, in a great degree, on the habitual exercise of this act. Its surprising influence, in improving the perceptive powers, is manifest in persons, who have been led, by their peculiar callings, or by necessity, to place uncommon reliance on a particular sense.

Thus sailors, who are accustomed to look at distant objects, acquire the power of seeing and distinguishing things, which, by reason of their distance, are invisible to common eyes/ Musicians become capable of discerning the minutest difference in sounds. Cooks and epicures acquire an uncommon sensibility in tasting and smelling ; and blind persons improve the sense of feeling to such a degree, as to make it, in some measure, supply the want of ;sight. These effects are produced chiefly by an increased and habitual attention, which

* A seafaring life, especially when early commenced, has a tendency to produce some physical change in the organ of vision.

20 ATTENTION.

enables those persons to notice impressions, which are so slight and languid, as wholly to escape the observation of others.

10. Attention is considered* a voluntary act of the mind, but it is not at all times equally subject to our command, and in young children is wholly involuntary. Extraordinary occurrences, which awaken curiosity, and things, which interest us in a high degree, by exciting some violent passion or emotion, often draw the attention so strongly, that we are unable for a time to transfer it to any other subject. So intensely are we sometimes engaged, that we lose our account of time, and take no notice of the objects, which strike the senses.

11. Attention is so essential to memory, that, without some degree of it, no thought could ever be recalled ; and the reason why we commit things to memory more easily at one time, than another, is, that we command our attention more perfectly. It is equally necessary in every operation of comparing, judging, and reasoning. Dr. Reid has remarked, " that, if * there be any thing that can be called genius,

* Stewart, Elements of the Philosophy of the Mind, vol. i. ch. 2 Reid, Essays on the Active Powers, Essay II. ch. 3.

COMPARING. 21

" in matters of mere judgment and reasoning, " it seems to consist chiefly in being able to " give that attention to the subject, which keeps " it steady in the mind, till we can survey it " accurately on all sides. There is a talent " of imagination, which bounds from earth to " heaven, and from heaven to earth, in a mo- "ment. This may be favourable to wit and " imagery ; but the powers of judging and rea- " soning depend chiefly on keeping the mind " to a clear and steady view of the subject."*

Chapter Third. /*\ Comparing

12. When the mind contemplates two things in reference to each other, ft performs the operation of comparing. Thus, when we say iron is harder than lead, and lead is heavier than iron, we compare these two substances with respect to the degrees, in which they possess the qualities of weight and hardness. From this operation we derive all our notions of relation ; as father, cousin, largeness, smallness, superiority, subjection, and the like.

* Essays on the Active Powers, Essay II. ch. 3.

22 COMPARING.

We make comparisons with the greatest ease, and frequently without being conscious of them. It is only by this operation, that we are enabled to recognise the objects, which we have before known, or to give to any quality or object an appropriate name ; for the application of the name requires not only the sensation, produced by a present object, but the comparison of that sensation with one formerly felt.*

13. This operation is performed by children in their earliest efforts at speech. It is by successively comparing the sounds, they utter, with those, made by others, that they learn to pronounce the words of their native tongue. That propensity to imitation, which is always conspicuous in the sports of children, is happily calculated to improve this effort of the mind. The same may be asserted of many of those studies, which usually occupy the years of childhood, and particularly of the study of foreign languages. Translations from one language into another require a constant and careful comparison of the corresponding words of different languages ; an exercise doubly

* Stewart, Elements, vol. i. ch. 3,

ABSTRACTION. 23

important to children, as it serves to improve their discerning faculties, and at the same time leads them to ascertain the exact import of words. The correctness of every process of judgment and reasoning depends, immediately or ultimately, on the accuracy of our comparisons.

- »V CHAPTER FOURTH.

ABSTRACTION.

14. Abstraction literally implies the separating of one thing from another ; but, as a mental operation, it denotes only a partial consideration of any thing. It is the act of considering one or more of the properties or circumstances of an object, apart from the rest. Thus we may consider the length of a bridge, without regarding its breadth or construction. We may sp6ak of fluidity in water, hardness in marble, or sweetness in sugar, without noticing the other properties of those substances. As the quality, thus mentally separated from those existing with it, may be found in numerous subjects, the name applied to it becomes a general term. So whiteness stands for the

24 ABSTRACTION.

colour of snow, milk, chalk, paper, and many other things.

15. This power, which the mind has, of separating the qualities combined in the objects, which fall under our observation, and of tracing the same quality in a multitude of objects, is the foundation of all classification, and gives rise to the general words of knguage. But, notwithstanding the necessity of abstraction in every act of classification, it may be performed on individuals, without referring them to any class. This has occasioned some* to suppose, that the formation of classes required a distinct operation, which they called generalization. Dr. Reid says, "we cannot " generalize without some degree of abstrac- " tion, but I apprehend we may abstract without " generalizing. For what hinders me from at- " tending to the whiteness of the naper before " me, without applying that colour to any other " object ? The whiteness of this individual " object is an abstract conception ; but not a " general one, while applied to one individuai " only. These two operations, however, are

* Reid, Intellectual Powers, Essay V. ch. 3. Collar d, Logick, part I. ch. 2.

ASSOCIATION. 25

<c subservient to each other ; for the more at- " tributes we observe and distinguish in any " one individual, the more agreements we shall " discover between it and other individuals. 1 '

Chapter Fifth. Association

16. By the association of ideas is understood that connexion among the thoughts, affections, and operations of the mind, by which one has a tendency to introduce another. That one idea is often suggested to the mind by another, and that sensible objects revive past trains of thought, are facts familiar to all. Words recall the objects, to which they have been applied ; and the objects as readily suggest their names. A long train of associated thoughts is sometimes introduced by a single circumstance. The view of the spot, where we passed the first years of life, after a long absence, will recall many interesting events of childhood. The first notes of a familiar tune, being sounded, will cause the remaining notes to pass through the mind in regular order.

17. No principle of our nature is productive of more important effects, than this, which

26 ASSOCIATION.

establishes a connexion between our ideas, feelings, and mental operations. It is the source of numerous errors and prejudices. It is the foundation of all our local attachments ; and of most of our prepossessions in behalf of the government and other institutions of our country. It is to the principle of association, that we are to attribute our predilections for the modes of dress, pronunciation, and behaviour of those, whom we esteem and respect.

The principles of association have been differently stated. Their number is not settled ; but the following are among the most obvious :

18. First, resemblance or analogy is an extensive principle of association. We are often reminded of one person, by the countenance, voice, or gestures of another. One natural scene suggests another ; and one event or one anecdote frequently brings another to our remembrance, by the similarity we observe between them.

19. Secondly, opposition or contrast is another principle of association, but of less extensive influence than the preceding. The pains of hunger and thirst suggest the pleasures of eating and drinking. Cold reminds us of

ASSOCIATION. 27

heat ; darkness, of light ; and parsimony, of prodigality. So,- among contending parties, extravagance on one side usually drives the other to the opposite extreme.

20. Thirdly, another, and with the bulk ot mankind the most extensive, ground of as sociation, is contiguity or nearness of time and place. The recollection of an event, in which we were interested, brings to our thoughts many circumstances connected with it ; as the place we were in, when it happened, or when we were informed of it ; the persons, who were with us ; and the peculiar state of our feelings at the time. The objects we meet on a road, that we have formerly travelled, successively remind us of the subjects, about which we were employed, when we passed them before.

21. A fourth principle of association results from the relations of cause and effect, premises and consequences. The sight of a surgical instrument, or an engine of torture, excites a strong sense of the pain, it is calculated to occasion ; and the sight of a wound reminds us of the instrument, by which it was made. When we see a fellow being in distress* we are solicitous to find out the cause ; and

28 ANALYSIS.

when we have afflictive tidings to communicate, we anticipate the grief, which will be excited. 22. As one idea may be associated with several others, each leading to a different series, it is obvious, that the same circumstance may suggest different trains of thought to different persons, and to the same person at different times. The association of ideas is concerned in every act of memory and recollection. No thought, after it has once passed from the mind, could ever be recalled, were it not for the tendency of one idea to introduce another.*

Chapter Sixth. Analysis

23. Analysis deserves a place among the operations, by which the elements of knowledge are acquired. Without this, our perceptive powers would give us only confused and imperfect notions of the objects around us. To analyze is nothing more, than to distinguish successively the several parts of any compound subject Nature dictates this process. We

* Hume, Essays, vol. ii. sect. 3. Stewart, Elem. vol. i. ch. 5. Beattie, Dissertations, Mor. and Crit. vol. i. ch. 2, sect. i. Scott Elem. Intel. Phil. ch. v. 6ect. i.

ANALYSIS. 29

commence it at the earliest period of improvement, and practise it in all our efforts to obtain information. The objects, which nature presents to us, consist of assemblages of different qualities, some more and others less easily distinguished. Children early become acquainted with the distinguishing properties of the things, daily offered to their senses, and in a few years find out the characteristick marks of numerous classes of things, and learn the use of language.

24. Things, which have no immediate reference to material objects, such as thoughts, affections, and mental operations, are analyzed in the same manner as objects of sense. The words abstract and reason denote processes of thought, each of which may be readily distinguished into separate parts, and these parts into others more remote. The same may be said of moral qualities, as justice, prudence, benevolence, and the like. In these, as in sensible objects, there are certain parts, which are instantly noticed, and others, which are discovered by attentive observation. The analysis begins in both cases with the leading 3*

30 ANALYSIS.

qualities, and becomes more perfect as new qualities are discovered.

25. We employ analysis in interpreting symbolical language and ambiguous propositions. Analysis enables us to investigate causes by their effects, and to find out the means necessary to attain an end proposed, by having the end first in view. It is by this instrument, that the chymist and botanist retrace the processes of nature, and ascertain the qualities of mineral and vegetable substances.

Analysis will be further considered under the head of Inductive Reasoning.*

* Condillac, Logick, part i. Watts, Logick, part iv. ch. 1. Stewart, Elem. vol. ii. ch. 4.

Chapter First. Logical Distinctions Of Terms

26. Words possess no natural aptness to denote the particular things, to which they are applied, rather than others, but acquire this aptness wholly by convention. Had the connexion between the name and the thing been established by nature, there would have been but one language in the world. But we find different words employed in different countries, and with equal advantage, to signify the same thing. Thus white, albus, and blanc, denote the same colour. The principal distinctions of terms in logick are the following :

27. First, terms are either simple or complex. A simple term is a single word ; as man, horse, tree. A complex term consists of two or more words, representing some object or association, formed to be the subject or predicate of a proposition ;* as, human fortitude, a swift

* See ch. 3.

horse, an amiable deportment. A word, which denotes several individuals of the same sort, is called a collective term ; as, army, forest, drove.

28. Secondly, terms are distinguished into absolute and relative. An absolute term is one* which represents an object or quality, without intimating its relation to any other thing ; as, man, river, mountain, roundness, strength. A relative term denotes an object so far only as it is connected with some other object. Thus, father implies a man primarily, as he is considered the cause of existence to another individual, denominated, in reference to him, son. These two terms, intimating each other, by a reciprocal reference, are called correlative. So patron and client, husband and wife, guardian and ward, are correlative terms.

There are other relative terms, as who which, it, that, and the like, which barely recall certain other words, before mentioned ; hence the words they refer to are denominated antecedents.

29. Thirdly, terms are distinguished into univocal, equivocal, and synonymous. Univocal terms are such as have invariably the same signification annexed to them. Thus individuality, genus, electricity, are univocal terms ; for they always signify the same things. Equivocal words are such as are employed in different senses. Of this sort is the word head, which may signify a part of a nail, of an animal, or of a discourse. So the words post and shore are equivocal ; for they are used in various senses.

That some words should be used in different senses is unavoidable, on account of the scantiness of language, which does not afford a distinct name for every idea. Notwithstanding this, we sometimes find two or more words applied to the same thing ; as wave and billow, dwelling and habitation. These are called synonymous terms.

30. A fourth distinction of terms is into abstract and concrete. An abstract term is one, which signifies some quality or attribute, without referring to any subject, in tvhich it may be found; as roundness, hardness, equality, firmness. Concrete terms denote both the attributes and the subjects, to which they belong. Sometimes they express the subjects directly, and the attributes indirectly ; and sometimes the reverse Thus philosopher, statesman, mechanick, are concrete terms, which directly denote persons, and indirectly the attributes, for which they are distinguished. But wise, valiant, swift, hard, are concretes, immediately signifying certain attributes, and indirectly intimating the persons or things, to which they belong.

31. Fifthly, terms are either singular or universal. A singular term is the proper name of some individual person, place, or thing ; as Alexander, London, Danube, Etna. Proper names are given only to those things, which we have frequent occasion to mention, as individuals. The design of proper names is to represent these, apart from the classes, to which they belong. Any term, that does this office, is a proper name ; and loses not its character as such by being applied, as it frequently is, to several individuals of the same kind, as Peter, John, William,

32. Universal terms, otherwise denominated common or appellative, are names indiscriminately applicable to many individual beings, whether natural or artificial, by reason of certain properties, which they possess in common. Thus man, city, river, mountain, are universal terms, because they a gree to all men, cities, rivers, and mountains.

33, Universal terms make the greatest part of the words of every language. Their signification is designedly imperfect ; comprising only the most common and obvious properties of things. They are abridgments of language, happily contrived to facilitate and expedite the intercourse of society. Every production of nature and art, and every property of mind and body, is an individual. Each has some properties peculiar to itself; and others, which it possesses in common with many other beings. By discarding the peculiar properties, and retaining under distinct names those, which are common, we reduce to a limited number of classes the innumerable objects, which fall under our observation. This distribution of* things into classes forms what logicians call the genera and species of things.

34. Species denotes a sort or class, including only individuals , and genus a class including under it two or more species, A species is formed by applying a name to that property, or collection of properties, in which many individuals are found to agree. Thus man is a species ; for the name is applicable to an indefinite number of individual beings, on account of their agreeing in the essential properties of an erect figure, and the faculties of speech and reason. So horse, deer, eagle, tree, are species. Genus implies the property or properties, which different species possess in common. Thus the property of walking on four feet is the foundation of the genus quadruped, which applies to horse, lion, dog, elephant, and many other species. So bird is a genus, of which eagle, lark, swan, and sparrow, are species.

35. In the distribution of things into genera and species, regard is had to the comprehension and extension of general terms. By the comprehension of a term is meant the aggregate of all the known properties of that thing, or class of things, to which it is applied. Thus gold includes in its comprehension a material substance, a yellow colour, superior weight, ductility, fusibility, and every other known property of that body. The extension oj a term regards the number of individual subjects, to which it may be applied. So the term gold includes in its extension every separate parcel of that metal. Man includes in its extension every individual of the human race.