A Textbook of Logic (5th Revised edition)

The present book is the fourth enlarged edition of the earlier book A Textbook of Logic — An Introduction. The current edition includes an additional chapter on Uses of Language and its Functions. Like the earlier book, the present book sets forth the principles and procedures of elementary Logic in the most simplified way and is specifically designed and intended for the use of undergraduate students. It contains almost all the main topics on Deductive, Inductive and Symbolic Logic prescribed in the syllabi of different universities in the country.

The book attempts to present a clear perspective on Logic as a science of correct reasoning. In the introductory chapter the aim of Logic and the task of a Logician are elaborated. Other topics covered here are Terms, Propositions, Immediate Inference, Syllogism, Boolean Equations, Venn Diagrams, Anti-Logism Theorem, Truth Functions, Truth Table, Deductive Method, Predicate Calculus, Scientific Inductions, Causation, Mill’s Methods and Informal Fallacies to mention a few. All the topics are explained with the help of diagrams and lucid examples. Each chapter is followed by plenty of exercises for the benefit of students.

Dr (Mrs.) Krishna Jain obtained her Masters Degree and PhD in Philosophy from Delhi University. She has been teaching Logic to the undergraduates for nearly the last three decades and is presently Reader in the Department of Philosophy, Janki Devi Memorial College, University of Delhi. Her other publications include Description in Philosophy — with Special Reference to Husserl and Wittgenstein (1994). 2007, Fourth revised and enlarged edition, xv, .348 p.; Bibliography; 22cm.

This fourth edition is yet another revised and enlarged edition of the earlier A Text book of Logic — An Introduction. Since incorrect use of language is one of the reasons for fallacious reasoning it is necessary for a student to understand the use of right language in the formulation and evaluation of arguments. Therefore, a new chapter on “Uses and Functions of Language” has been included in the present edition.

I am thankful to my colleagues Dr Sneh Khosla, Dr Rajib Ray Dr Raj Verma Sinha and Mansi Gupta for their help in many ways. I am equally thankful to Shri Susheel Kumar Mittal of the D.K. Printworld, Delhi for his keenness and personal interest shown in publishing this edition of the book.

This is another revised edition of the earlier A Textbook of Logic – An Introduction (Revised and Enlarged Edition). Two new chapters, “Formal Proof of Validity” and Predicate Calculus”, have been added. Plenty of exercises have been given for the students to practice.

This is an enlarged and revised edition of the earlier A Textbook of Logic — An Introduction. It contains, besides a new chapter n “Laws of Thought”, many fresh exercises. I am confident that his new edition will serve the interest of the students better.

I am extremely grateful to my numerous friends, colleagues and students for their valuable and constructive suggestions and comments on the earlier edition of the text.

The present book is the outcome of an interaction with students over a long period of time and proposes to explain the principles and procedures of Elementary Logic in the simplest possible way. It is an attempt to introduce students to both traditional as well as Symbolic Logic. It also covers Inductive Logic and includes Informal Fallacies committed in everyday arguments.

Almost all the topics are explained with the help of lucid examples. They also carry plenty of exercises for a better grasp of the subject. Special attempts have been made to clarify basic concepts such as Validity, Reasoning, Types of Reasoning, Proposition, Term, etc. In modern logic, Existential Import, Boolean Alzebra, Venn Diagrams, Truth Table, Shorter Truth Table Method are explained in a simple and easy language. A special chapter is provided for “translating” ordinary language sentences into symbolism of modern logic.

I shall like to express my gratitude to Prof. V.K. Bhardwaj, Deptt. of Philosophy, Delhi University, who went through the first draft of the text and offered many valuable suggestions. I am also thankful to Shri Balwant of Ajanta Books International for his keen interest in publishing the book. Last but not the least my thanks are due to my husband Dr V.K. Jam for encouraging me to write the present text.

Logic is a science of reasoning. The aim of logic is to provide methods, techniques and devices which help in differentiating right reasoning from wrong, and good reasoning from bad. But it does not mean that only those who study logic can reason correctly. However, it is true that those who study logic certainly make less errors while arguing. Just as a trained athlete is a better player than an untrained one, similarly a person acquainted with logical principles is likely to put forth good arguments. Knowledge of logic helps one to face a problem in a more orderly and systematic way, and in many cases makes the solution less difficult but more certain.

Science means a branch of coherently organized body of knowledge. Since logic is the study of consistent reasoning, it is certainly a science. Through logic we can judge, for example, whether a piece of reasoning such as we find in newspapers, magazines, etc. is correct or not, and also whether the conclusion follows correctly from the given evidences. Correct reasoning ns to discover the right order between the evidences and conclusion. There is order and sequence in our reasoning. The moment one is concerned with the idea that one thought follows from another, he is being logical. Correct and consistent reasoning means conclusion follows from the evidences or the premisses. In other words, correct reasoning means the premisses are strong enough to support the conclusion, and when the premisses are insufficient or inadequate to support the conclusion then the reasoning becomes incorrect.

Correct reasoning is the basis of all sciences, natural as well as social. In this sense it is very true to say that logic is presupposed by all sciences, and hence, it becomes a basic and primary science; a science of sciences.

But the logicians are not interested merely in the study of methods or techniques of differentiating right reasoning from wrong; it is equally important for them to acquire skill to apply these methods in determining the correctness of everyday reasoning and discourse as well. How efficiently or how skillfully one makes use of these methods in practical life is nothing but demonstrating the artistic aptitude. All arts are concerned with “doing” and “making”. Anyone who knows logic “does” good reasoning and “makes” sound arguments. He makes good definitions and good debates. Logic prepares a man to make right reasoning and right decisions. “Practice makes a man prefect” is true for all arts, and it is equally true for logic as well.