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A System of Logic, Ratiocinative and Inductive

John Stuart Mill

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A System of Logic, Ratiocinative and Inductive is a book by English philosopher John Stuart Mill, first published in 1843. An important work in the philosophy of science, it lays out Mill's five principles of inductive reasoning, and is divided into six books: Of Names And Propositions; On Reasoning; Of Induction; Of Operations Subsidiary To Induction; On Fallacies; and, On The Logic Of The Moral Sciences. Full chapter list.

№ 70 in Anne Haight's List of Banned Books.

This book has 648 pages in the PDF version, and was originally published in 1843. This is based on an 1882 edition.

Production notes: This edition of A System of Logic, Ratiocinative and Inductive was published by Global Grey ebooks on the 14th July 2021. The artwork used for the cover is 'John Stuart Mill' by George Frederic Watts.

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Excerpt from 'A System of Logic, Ratiocinative and Inductive'

§ 1. There is as great diversity among authors in the modes which they have adopted of defining logic, as in their treatment of the details of it. This is what might naturally be expected on any subject on which writers have availed themselves of the same language as a means of delivering different ideas. Ethics and jurisprudence are liable to the remark in common with logic. Almost every writer having taken a different view of some of the particulars which these branches of knowledge are usually understood to include; each has so framed his definition as to indicate beforehand his own peculiar tenets, and sometimes to beg the question in their favor.

This diversity is not so much an evil to be complained of, as an inevitable and in some degree a proper result of the imperfect state of those sciences. It is not to be expected that there should be agreement about the definition of any thing, until there is agreement about the thing itself. To define, is to select from among all the properties of a thing, those which shall be understood to be designated and declared by its name; and the properties must be well known to us before we can be competent to determine which of them are fittest to be chosen for this purpose. Accordingly, in the case of so complex an aggregation of particulars as are comprehended in any thing which can be called a science, the definition we set out with is seldom that which a more extensive knowledge of the subject shows to be the most appropriate. Until we know the particulars themselves, we can not fix upon the most correct and compact mode of circumscribing them by a general description. It was not until after an extensive and accurate acquaintance with the details of chemical phenomena, that it was found possible to frame a rational definition of chemistry; and the definition of the science of life and organization is still a matter of dispute. So long as the sciences are imperfect, the definitions must partake of their imperfection; and if the former are progressive, the latter ought to be so too. As much, therefore, as is to be expected from a definition placed at the commencement of a subject, is that it should define the scope of our inquiries: and the definition which I am about to offer of the science of logic, pretends to nothing more than to be a statement of the question which I have put to myself, and which this book is an attempt to resolve. The reader is at liberty to object to it as a definition of logic; but it is at all events a correct definition of the subject of this volume.

§ 2. Logic has often been called the Art of Reasoning. A writer who has done more than any other person to restore this study to the rank from which it had fallen in the estimation of the cultivated class in our own country, has adopted the above definition with an amendment; he has defined Logic to be the Science, as well as the Art, of reasoning; meaning by the former term, the analysis of the mental process which takes place whenever we reason, and by the latter, the rules, grounded on that analysis, for conducting the process correctly. There can be no doubt as to the propriety of the emendation. A right understanding of the mental process itself, of the conditions it depends on, and the steps of which it consists, is the only basis on which a system of rules, fitted for the direction of the process, can possibly be founded. Art necessarily presupposes knowledge; art, in any but its infant state, presupposes scientific knowledge: and if every art does not bear the name of a science, it is only because several sciences are often necessary to form the groundwork of a single art. So complicated are the conditions which govern our practical agency, that to enable one thing to be done, it is often requisite to know the nature and properties of many things.

Logic, then, comprises the science of reasoning, as well as an art, founded on that science. But the word Reasoning, again, like most other scientific terms in popular use, abounds in ambiguities. In one of its acceptations, it means syllogizing; or the mode of inference which may be called (with sufficient accuracy for the present purpose) concluding from generals to particulars. In another of its senses, to reason is simply to infer any assertion, from assertions already admitted: and in this sense induction is as much entitled to be called reasoning as the demonstrations of geometry.

Writers on logic have generally preferred the former acceptation of the term: the latter, and more extensive signification is that in which I mean to use it. I do this by virtue of the right I claim for every author, to give whatever provisional definition he pleases of his own subject. But sufficient reasons will, I believe, unfold themselves as we advance, why this should be not only the provisional but the final definition. It involves, at all events, no arbitrary change in the meaning of the word; for, with the general usage of the English language, the wider signification, I believe, accords better than the more restricted one.

§ 3. But reasoning, even in the widest sense of which the word is susceptible, does not seem to comprehend all that is included, either in the best, or even in the most current, conception of the scope and province of our science. The employment of the word Logic to denote the theory of Argumentation, is derived from the Aristotelian, or, as they are commonly termed, the scholastic, logicians. Yet even with them, in their systematic treatises, Argumentation was the subject only of the third part: the two former treated of Terms, and of Propositions; under one or other of which heads were also included Definition and Division. By some, indeed, these previous topics were professedly introduced only on account of their connection with reasoning, and as a preparation for the doctrine and rules of the syllogism. Yet they were treated with greater minuteness, and dwelt on at greater length, than was required for that purpose alone. More recent writers on logic have generally understood the term as it was employed by the able author of the Port Royal Logic; viz., as equivalent to the Art of Thinking. Nor is this acceptation confined to books, and scientific inquiries. Even in ordinary conversation, the ideas connected with the word Logic include at least precision of language, and accuracy of classification: and we perhaps oftener hear persons speak of a logical arrangement, or of expressions logically defined, than of conclusions logically deduced from premises. Again, a man is often called a great logician, or a man of powerful logic, not for the accuracy of his deductions, but for the extent of his command over premises; because the general propositions required for explaining a difficulty or refuting a sophism, copiously and promptly occur to him: because, in short, his knowledge, besides being ample, is well under his command for argumentative use. Whether, therefore, we conform to the practice of those who have made the subject their particular study, or to that of popular writers and common discourse, the province of logic will include several operations of the intellect not usually considered to fall within the meaning of the terms Reasoning and Argumentation.

Chapter List for 'A System of Logic, Ratiocinative and Inductive'

Preface To The First Edition

Preface To The Third And Fourth Editions



Chapter 1. Of The Necessity Of Commencing With An Analysis Of Language

Chapter 2. Of Names

Chapter 3. Of The Things Denoted By Names

Chapter 4. Of Propositions

Chapter 5. Of The Import Of Propositions

Chapter 6. Of Propositions Merely Verbal

Chapter 7. Of The Nature Of Classification, And The Five Predicables

Chapter 8. Of Definition


Chapter 1. Of Inference, Or Reasoning, In General

Chapter 2. Of Ratiocination, Or Syllogism

Chapter 3. Of The Functions And Logical Value Of The Syllogism

Chapter 4. Of Trains Of Reasoning, And Deductive Sciences

Chapter 5. Of Demonstration, And Necessary Truths

Chapter 6. The Same Subject Continued

Chapter 7. Examination Of Some Opinions Opposed To The Preceding Doctrines


Chapter 1. Preliminary Observations On Induction In General

Chapter 2. Of Inductions Improperly So Called

Chapter 3. Of The Ground Of Induction

Chapter 4. Of Laws Of Nature

Chapter 5. Of The Law Of Universal Causation

Chapter 6. On The Composition Of Causes

Chapter 7. On Observation And Experiment

Chapter 8. Of The Four Methods Of Experimental Inquiry

Chapter 9. Miscellaneous Examples Of The Four Methods

Chapter 10. Of Plurality Of Causes, And Of The Intermixture Of Effects

Chapter 11. Of The Deductive Method

Chapter 12. Of The Explanation Of Laws Of Nature

Chapter 13. Miscellaneous Examples Of The Explanation Of Laws Of Nature

Chapter 14. Of The Limits To The Explanation Of Laws Of Nature; And Of Hypotheses

Chapter 15. Of Progressive Effects; And Of The Continued Action Of Causes

Chapter 16. Of Empirical Laws

Chapter 17. Of Chance And Its Elimination

Chapter 18. Of The Calculation Of Chances

Chapter 19. Of The Extension Of Derivative Laws To Adjacent Cases

Chapter 20. Of Analogy

Chapter 21. Of The Evidence Of The Law Of Universal Causation

Chapter 22. Of Uniformities Of Co-Existence Not Dependent On Causation

Chapter 23. Of Approximate Generalizations, And Probable Evidence

Chapter 24. Of The Remaining Laws Of Nature

Chapter 25. Of The Grounds Of Disbelief


Chapter 1. Of Observation And Description

Chapter 2. Of Abstraction, Or The Formation Of Conceptions

Chapter 3. Of Naming, As Subsidiary To Induction

Chapter 4. Of The Requisites Of A Philosophical Language, And The Principles Of Definition

Chapter 5. On The Natural History Of The Variations In The Meaning Of Terms

Chapter 6. The Principles Of A Philosophical Language Further Considered

Chapter 7. Of Classification, As Subsidiary To Induction

Chapter 8. Of Classification By Series


Chapter 1. Of Fallacies In General

Chapter 2. Classification Of Fallacies

Chapter 3. Fallacies Of Simple Inspection; Or A Priori Fallacies

Chapter 4. Fallacies Of Observation

Chapter 5. Fallacies Of Generalization

Chapter 6. Fallacies Of Ratiocination

Chapter 7. Fallacies Of Confusion


Chapter 1. Introductory Remarks

Chapter 2. Of Liberty And Necessity

Chapter 3. That There Is, Or May Be, A Science Of Human Nature

Chapter 4. Of The Laws Of Mind

Chapter 5. Of Ethology, Or The Science Of The Formation Of Character

Chapter 6. General Considerations On The Social Science

Chapter 7. Of The Chemical, Or Experimental, Method In The Social Science

Chapter 8. Of The Geometrical, Or Abstract, Method

Chapter 9. Of The Physical, Or Concrete Deductive, Method

Chapter 10. Of The Inverse Deductive, Or Historical, Method

Chapter 11. Additional Elucidations Of The Science Of History

Chapter 12. Of The Logic Of Practice, Or Art; Including Morality And Policy

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