Welcome to HSLC Guru! This page presents the complete Question and Answer solution for Class 11 Logic and Philosophy Chapter 1 — Logic: Definition, Nature, Scope, Utility, Traditional and Modern Logic, prepared strictly according to the latest ASSEB (Assam State School Education Board) Higher Secondary First Year syllabus. The chapter introduces students to the foundational discipline of Logic — its etymology, its classical definitions by great thinkers such as Aristotle, Mill, Whately, Bain, Joseph, Stebbing and Cohen-Nagel, and its place among the normative sciences. We have organised the material into a clear summary, textbook-based Very Short, Short and Long answer questions, and a rich bank of additional MCQs, fill-in-the-blanks, true/false and matching exercises. A detailed glossary and comparison tables (Truth vs Validity, Formal vs Material Truth, Deductive vs Inductive, Traditional vs Modern Logic, Logic vs Psychology vs Grammar vs Mathematics) round off the chapter so that learners can confidently approach board examinations.
Chapter Summary
Logic is the normative science of valid reasoning that investigates the principles of correct thinking, ensuring truth through systematic inference, evaluation of arguments and detection of fallacies.
The English word Logic is derived from the Greek term “Logos”, which means “thought as expressed in language” or simply “reason” and “word”. Logic is therefore the science that deals with thought, but not with every act of thinking — only with that organised thinking which produces inference. Different philosophers have defined Logic in different ways. Aristotle, the Father of Logic, treated it as the instrument (Organon) of all sciences. J. S. Mill defined Logic as “the science of the operations of the understanding which are subservient to the estimation of evidence”. Richard Whately called it “the science as well as the art of reasoning”. Alexander Bain regarded it as “the science of proof or evidence”. H. W. B. Joseph defined it as “the science which studies the general principles in accordance with which we think about real things”. L. S. Stebbing said Logic is “the science which investigates the general principles of valid thought”. Cohen and Nagel defined it as “the science of the most general laws of valid inference”.
The nature of Logic includes four important features. (i) Logic is concerned with mediate knowledge, that is, knowledge obtained through the medium of other knowledge, not with immediate sense-perception. (ii) Logic is concerned with both formal and material truth — that is, it studies the consistency of thought as well as its correspondence with reality. (iii) Logic is both a science and an art; as a science, it provides systematic knowledge of the principles of valid thinking, and as an art, it teaches the practical application of these principles. (iv) Logic is a normative science, not a positive one — it tells us how we ought to think in order to attain truth, and not how we actually think.
The scope of Logic covers the products of thinking — namely terms, propositions and inferences (arguments). Logic studies definition, division, classification, the laws of thought (Identity, Contradiction, Excluded Middle), the rules of valid deduction, the methods of induction, and the detection of fallacies. The utility of Logic is both theoretical and practical. It cultivates clear, precise and disciplined thinking; it removes prejudice, superstition and verbal confusion; it serves as a tool for every other science; it forms the basis of the scientific method; and it is indispensable for the courtroom, debate, philosophy and everyday decision-making.
Historically, Logic is divided into Traditional Logic and Modern (Symbolic) Logic. Traditional Logic, founded by Aristotle in his Organon, uses ordinary language, deals chiefly with categorical syllogisms and the four standard propositions (A, E, I, O), and is largely deductive. Modern Logic, developed by George Boole, Gottlob Frege, Bertrand Russell and A. N. Whitehead (in Principia Mathematica), uses artificial symbols and mathematical techniques. It is broader in scope, more exact and includes propositional and predicate calculus. The two are not opposed but represent different stages of the same intellectual journey toward perfect rigour. Logic is closely related to, yet distinct from, Psychology (which describes how we actually think), Grammar (which deals with correct language), and Mathematics (which uses logical reasoning but is concerned with quantity).
Textbook Questions and Answers
A. Very Short Answer Type Questions (1 Mark)
Q1. From which Greek word is the term “Logic” derived?
Answer: The term “Logic” is derived from the Greek word “Logos”.
Q2. What is the meaning of the Greek word “Logos”?
Answer: “Logos” means “thought as expressed in language” or “word, reason, discourse”.
Q3. Who is regarded as the Father of Logic?
Answer: Aristotle (384–322 B.C.) is regarded as the Father of Logic.
Q4. Who is called the Father of Symbolic Logic?
Answer: G. W. Leibnitz is regarded as the Father of Symbolic (Modern) Logic.
Q5. What is the ideal of Logic?
Answer: Truth is the ideal of Logic.
Q6. Is Logic a positive science or a normative science?
Answer: Logic is a normative science.
Q7. Is Logic a science, an art, or both?
Answer: Logic is both a science and an art.
Q8. What is the name of Aristotle’s collection of logical works?
Answer: Aristotle’s collection of logical writings is called the Organon.
Q9. Name the famous work of Russell and Whitehead on modern logic.
Answer: Their famous work is Principia Mathematica (1910–1913).
Q10. Who wrote the book “The Laws of Thought”?
Answer: George Boole wrote An Investigation of the Laws of Thought (1854).
Q11. Give one example of a normative science.
Answer: Ethics is an example of a normative science.
Q12. What does formal truth mean?
Answer: Formal truth means self-consistency or freedom from self-contradiction in thought.
Q13. What does material truth mean?
Answer: Material truth means the correspondence of thought with the actual facts of the world.
Q14. What is mediate knowledge?
Answer: Mediate knowledge is knowledge obtained through the medium of some other prior knowledge — i.e., through inference.
Q15. What kind of knowledge is the subject matter of Logic?
Answer: Mediate (inferential) knowledge is the subject matter of Logic.
B. Short Answer Type Questions (2–3 Marks)
Q1. Define Logic.
Answer: Logic is the normative science that studies the general principles of valid thought or correct reasoning. It investigates how we ought to think in order to arrive at truth, examining the structure of inferences, the validity of arguments and the laws of thought.
Q2. State J. S. Mill’s definition of Logic.
Answer: According to John Stuart Mill, “Logic is the science of the operations of the understanding which are subservient to the estimation of evidence.” Mill thus emphasises Logic’s role in evaluating proof and evidence in reasoning.
Q3. Give Whately’s definition of Logic.
Answer: Richard Whately defined Logic as “the science as well as the art of reasoning”. By calling it both a science and an art, he stressed that Logic gives us systematic knowledge of valid thinking and also teaches us how to think correctly in practice.
Q4. What is Bain’s definition of Logic?
Answer: Alexander Bain defined Logic as “the science of proof or evidence”. For Bain, Logic primarily deals with how a statement or conclusion is established by reasons.
Q5. State Cohen and Nagel’s definition of Logic.
Answer: Morris Cohen and Ernest Nagel defined Logic as “the science of the most general laws of valid inference”. This definition highlights Logic’s concern with universal principles applicable to every reasoning process.
Q6. Mention two utilities of studying Logic.
Answer: (i) Logic develops the habit of clear, accurate and disciplined thinking. (ii) It helps to detect fallacies and avoid errors in reasoning, thereby protecting us from prejudice, superstition and false beliefs.
Q7. Distinguish between immediate and mediate knowledge.
Answer: Immediate knowledge is knowledge gained directly through sense-perception, intuition or self-consciousness — for example, “I see the sun”. Mediate knowledge is gained indirectly through the medium of other knowledge, i.e., by reasoning — for example, inferring that “it rained last night” from seeing wet streets in the morning. Logic deals only with mediate knowledge.
Q8. Why is Logic called a Normative Science?
Answer: A normative science studies an ideal and lays down norms or standards by which actual practice should be judged. Logic is normative because it does not describe how people actually think; rather, it prescribes how one ought to think to attain truth. Its ideal is Truth, just as Ethics has the ideal of Goodness and Aesthetics that of Beauty.
Q9. Why is Logic regarded as both a science and an art?
Answer: Logic is a science because it provides systematic, organised knowledge of the principles and laws of valid reasoning. It is an art because it gives practical rules for the application of those principles, helping us actually to think correctly. Hence Whately rightly called it “the science as well as the art of reasoning”.
Q10. Distinguish between Formal and Material Truth.
Answer: Formal truth refers to the internal consistency of thought — an argument is formally true when its conclusion follows necessarily from its premises without contradiction. Material truth refers to the correspondence of thought with the actual world — a proposition is materially true when it agrees with facts. For example, “All men are mortal; Socrates is a man; therefore Socrates is mortal” is both formally and materially true.
Q11. State two points of difference between Traditional and Modern Logic.
Answer: (i) Traditional Logic uses ordinary language, while Modern (Symbolic) Logic uses artificial symbols and mathematical notation. (ii) Traditional Logic is mainly concerned with the categorical syllogism and the four standard propositions, whereas Modern Logic has a much wider scope, including propositional and predicate calculus.
Q12. What is meant by the scope of Logic?
Answer: The scope of Logic refers to the field or range of its subject matter. It includes terms, propositions and inferences (arguments); definition, division and classification; the laws of thought; deductive and inductive reasoning; and the detection of fallacies. Only mediate knowledge falls within the scope of Logic.
Q13. Distinguish between Truth and Validity.
Answer: Truth is a property of propositions — a proposition is true when it agrees with facts. Validity is a property of arguments — an argument is valid when its conclusion necessarily follows from its premises. A valid argument may have false premises, and a sound conclusion may emerge from invalid reasoning; hence the two concepts must be carefully distinguished.
Q14. Distinguish between Deductive and Inductive Inference.
Answer: In Deductive Inference, the conclusion necessarily follows from the premises and cannot go beyond them; it moves from the general to the particular (e.g., “All men are mortal; therefore Socrates is mortal”). In Inductive Inference, the conclusion goes beyond the premises by way of generalisation; it moves from particulars to the general (e.g., observing many crows being black and concluding “All crows are black”).
Q15. What are ideograms?
Answer: Ideograms are symbols which directly represent ideas or concepts rather than the sounds of words. In Modern Symbolic Logic, letters such as p, q, r and connectives such as ~ (negation), · (conjunction), ∨ (disjunction) and ⊃ (implication) function as ideograms because they stand directly for logical ideas, allowing exact and concise expression.
C. Long Answer Type Questions (5–6 Marks)
Q1. Discuss the nature of Logic.
Answer: The nature of Logic can be understood through the following four characteristics:
(i) Logic deals with mediate knowledge: Logic does not concern itself with immediate sense-perception or intuition. Its subject matter is reasoning — the process by which we arrive at new knowledge through the medium of already-known facts. The conclusion of an argument is mediate because it is reached through premises.
(ii) Logic is concerned with both Formal and Material Truth: Logic studies the consistency of thought (formal truth) as well as the correspondence of thought with reality (material truth). Deductive logic emphasises formal truth, while inductive logic seeks material truth.
(iii) Logic is both a Science and an Art: As a science, Logic systematises the principles of valid reasoning. As an art, it teaches the practical application of these principles to actual thinking. Whately famously called it “the science as well as the art of reasoning”.
(iv) Logic is a Normative Science: Unlike positive sciences such as Physics or Chemistry which describe what is, Logic prescribes what ought to be. Its ideal is Truth, and it lays down standards (norms) by which actual reasoning is to be judged. Together, these features make Logic a unique discipline that occupies a central place in human thought.
Q2. Describe the scope of Logic.
Answer: The scope of Logic refers to the area covered by its subject matter. The following points define the scope of Logic:
(i) Mediate knowledge alone falls within the scope of Logic. Immediate experiences such as sensations belong to Psychology, not Logic.
(ii) Logic is concerned with reasoning that is correct or valid; it does not study every act of thinking but only that thinking which leads to inference.
(iii) Logic deals primarily with the products of thought — terms, propositions and arguments — rather than with the psychological process of thinking.
(iv) The scope of Logic includes both Deductive and Inductive Inference. Deduction examines necessary conclusions from given premises; induction generalises from particular instances.
(v) Logic studies definition, division and classification, which are essential for clear thinking.
(vi) It examines the fundamental Laws of Thought — the laws of Identity, Contradiction and Excluded Middle.
(vii) Logic identifies and explains fallacies — errors that may occur in reasoning. Thus the scope of Logic is wide and forms the basis of every other intellectual discipline.
Q3. Explain the utility of studying Logic.
Answer: The utility of Logic is both theoretical and practical:
(i) Cultivation of correct thinking: Logic disciplines the mind and teaches us to think clearly, accurately and consistently.
(ii) Detection of fallacies: It enables us to identify errors in our own and others’ reasoning, thereby saving us from being misled.
(iii) Removal of prejudice and superstition: Logical training removes blind beliefs and replaces them with reasoned conviction.
(iv) Foundation of all sciences: Every science depends on inference and proof. Logic provides the methodology common to all sciences and is therefore called the “science of sciences”.
(v) Aid to clear language: Logic insists on precise definitions, removing verbal ambiguity from speech and writing.
(vi) Use in practical life: Lawyers, judges, debaters, scientists and statesmen all depend on logical reasoning. Even in ordinary decision-making, Logic helps us weigh evidence and choose wisely.
(vii) Self-knowledge: By compelling us to examine our own thought processes, Logic contributes to intellectual honesty and self-improvement. Hence Logic has been rightly described as the “torchlight of knowledge”.
Q4. Distinguish between Traditional and Modern (Symbolic) Logic.
Answer: Traditional Logic, founded by Aristotle, and Modern (Symbolic) Logic, developed by Boole, Frege, Russell and Whitehead, differ in the following respects:
| Point | Traditional Logic | Modern (Symbolic) Logic |
|---|---|---|
| Founder | Aristotle | Leibnitz, later Boole, Frege, Russell-Whitehead |
| Language | Uses ordinary language | Uses artificial symbols and notation |
| Subject matter | Mainly the categorical syllogism and four standard propositions (A, E, I, O) | Propositional calculus, predicate calculus, relations, classes, etc. |
| Scope | Narrow — limited to subject-predicate form | Wide — covers many forms of reasoning |
| Method | Mostly deductive, qualitative | Both deductive and quantitative; uses mathematical methods |
| Exactness | Less exact due to ambiguity of language | More exact due to use of unambiguous symbols |
| Time period | Long history (since 4th century BC) | Recently developed (mid-19th century onwards) |
| Aim | Mainly material truth | Mainly formal truth and validity |
However, the two are not opposed; Modern Logic is a developed and more refined form of Traditional Logic, representing a different stage of the same intellectual journey.
Q5. Define Formal and Material Truth with examples and state three differences between them.
Answer: Formal Truth means self-consistency or freedom from contradiction in thought. An argument is formally true when its conclusion follows from its premises according to logical rules, irrespective of whether the premises are factually correct. Example: “All cats can fly; Tom is a cat; therefore Tom can fly.” This argument is formally true (valid) because the conclusion follows from the premises, even though the first premise is factually false.
Material Truth means the agreement of thought with reality — the correspondence of a proposition with actual facts. Example: “Water boils at 100°C at sea level” is materially true because it corresponds to the way the world actually is.
| Point | Formal Truth | Material Truth |
|---|---|---|
| Meaning | Self-consistency of thought | Correspondence of thought with reality |
| Concerned with | The form/structure of reasoning | The content/matter of reasoning |
| Studied chiefly by | Deductive Logic | Inductive Logic / experimental sciences |
| Test | Logical consistency | Agreement with facts |
| Example | “All A is B; All B is C; therefore All A is C” | “The earth revolves round the sun” |
Q6. Discuss the relation between Logic and other related sciences (Psychology, Grammar and Mathematics).
Answer: (a) Logic and Psychology: Both deal with thought, but Psychology is a positive science describing how we actually think (mental processes such as perception, memory, imagination), while Logic is a normative science prescribing how we ought to think to attain truth. Psychology studies thought as a fact; Logic studies thought as a norm.
(b) Logic and Grammar: Both are normative and concerned with language. Grammar gives rules for the correct use of words and sentences in a given language; Logic gives rules for valid reasoning irrespective of language. Grammar deals with form of expression; Logic with form of thought.
(c) Logic and Mathematics: Both are formal and deductive sciences using symbols. Mathematics is concerned chiefly with quantity (number, magnitude), while Logic is concerned with the most general principles of valid inference applicable to any subject. Modern Symbolic Logic is closely allied to Mathematics — Russell and Whitehead’s Principia Mathematica tried to derive Mathematics from Logic.
Additional Practice Questions
Multiple Choice Questions (MCQs)
1. The word “Logic” is derived from the Greek word —
(a) Logos (b) Logia (c) Logus (d) Logon
Answer: (a) Logos
2. Who is regarded as the Father of Logic?
(a) Plato (b) Aristotle (c) Socrates (d) Bacon
Answer: (b) Aristotle
3. The ideal of Logic is —
(a) Beauty (b) Goodness (c) Truth (d) Utility
Answer: (c) Truth
4. Logic is a —
(a) Positive science (b) Normative science (c) Empirical science (d) Natural science
Answer: (b) Normative science
5. Logic is —
(a) Only a science (b) Only an art (c) Both a science and an art (d) Neither a science nor an art
Answer: (c) Both a science and an art
6. The collection of Aristotle’s logical treatises is known as —
(a) Republic (b) Organon (c) Metaphysics (d) Novum Organum
Answer: (b) Organon
7. Who is called the Father of Symbolic Logic?
(a) George Boole (b) G. W. Leibnitz (c) Bertrand Russell (d) Gottlob Frege
Answer: (b) G. W. Leibnitz
8. The book “Principia Mathematica” was written by —
(a) Russell and Whitehead (b) Boole and Frege (c) Mill and Bain (d) Cohen and Nagel
Answer: (a) Russell and Whitehead
9. Logic is concerned with —
(a) Immediate knowledge (b) Mediate knowledge (c) Sensation (d) Imagination
Answer: (b) Mediate knowledge
10. “Logic is the science of the operations of the understanding subservient to the estimation of evidence” — this definition was given by —
(a) Aristotle (b) J. S. Mill (c) Whately (d) Bain
Answer: (b) J. S. Mill
11. Formal truth means —
(a) Correspondence with facts (b) Self-consistency of thought (c) Sense-experience (d) Beauty
Answer: (b) Self-consistency of thought
12. Material truth means —
(a) Self-consistency (b) Logical form (c) Correspondence of thought with reality (d) None of the above
Answer: (c) Correspondence of thought with reality
13. Which of the following is a normative science?
(a) Physics (b) Chemistry (c) Logic (d) Biology
Answer: (c) Logic
14. The three traditional Laws of Thought are Identity, Contradiction and —
(a) Causation (b) Excluded Middle (c) Sufficient Reason (d) Uniformity
Answer: (b) Excluded Middle
15. Modern Symbolic Logic uses —
(a) Ordinary language (b) Artificial symbols (c) Diagrams only (d) Numbers only
Answer: (b) Artificial symbols
16. Which of the following is the subject matter of Logic?
(a) Term, Proposition and Inference (b) Memory and Imagination (c) Pleasure and Pain (d) Beauty
Answer: (a) Term, Proposition and Inference
17. Which kind of inference moves from the general to the particular?
(a) Inductive (b) Deductive (c) Analogical (d) Probable
Answer: (b) Deductive
18. Validity is a property of —
(a) Propositions (b) Arguments (c) Sensations (d) Words
Answer: (b) Arguments
19. “Logic is the science of proof or evidence” — this definition was given by —
(a) Mill (b) Bain (c) Whately (d) Joseph
Answer: (b) Bain
20. Which of the following is NOT within the scope of Logic?
(a) Inference (b) Proposition (c) Immediate sensation (d) Term
Answer: (c) Immediate sensation
Fill in the Blanks
1. The word Logic is derived from the Greek word _____.
Answer: Logos
2. Logic is a _____ science.
Answer: Normative
3. Logic is both a science and an _____.
Answer: Art
4. The ideal of Logic is _____.
Answer: Truth
5. _____ is regarded as the Father of Logic.
Answer: Aristotle
6. _____ is regarded as the Father of Symbolic Logic.
Answer: Leibnitz
7. Aristotle’s collection of logical works is called _____.
Answer: Organon
8. The famous book of Russell and Whitehead is _____.
Answer: Principia Mathematica
9. Logic deals with _____ knowledge.
Answer: Mediate
10. _____ truth means correspondence with reality.
Answer: Material
11. _____ truth means self-consistency of thought.
Answer: Formal
12. The three subject matters of Logic are term, _____ and inference.
Answer: Proposition
13. Modern Logic uses _____ instead of ordinary language.
Answer: Symbols
14. The Law of _____ states “A is A”.
Answer: Identity
15. Validity is a property of _____.
Answer: Arguments
True or False
1. Logos means thought as expressed in language. Answer: True
2. Logic is a positive science. Answer: False (it is normative)
3. Aristotle wrote the Organon. Answer: True
4. Logic deals with immediate knowledge. Answer: False
5. Symbolic Logic is a developed form of Classical Logic. Answer: True
6. Leibnitz can be called the father of Symbolic Logic. Answer: True
7. Logic is only a science, not an art. Answer: False
8. Truth is the ideal of Logic. Answer: True
9. Material truth means consistency of thought. Answer: False
10. Logic and Psychology have the same subject matter. Answer: False
11. Modern Logic is closely allied to Mathematics. Answer: True
12. Term, proposition and inference are the subject matters of Logic. Answer: True
Matching
| Column A | Column B |
|---|---|
| 1. Aristotle | (a) Father of Symbolic Logic |
| 2. Leibnitz | (b) Father of Logic |
| 3. J. S. Mill | (c) Principia Mathematica |
| 4. Russell-Whitehead | (d) Science of evidence-estimation |
| 5. Bain | (e) Science of proof or evidence |
| 6. Boole | (f) Laws of Thought (1854) |
Answers: 1 — (b); 2 — (a); 3 — (d); 4 — (c); 5 — (e); 6 — (f)
Glossary of Key Terms
| Term | Meaning |
|---|---|
| Logic | The normative science of valid reasoning |
| Logos | Greek root meaning thought, word or reason |
| Organon | Aristotle’s collection of logical treatises |
| Normative Science | Science that prescribes ideals and norms (Logic, Ethics, Aesthetics) |
| Positive Science | Science that describes facts as they are (Physics, Chemistry) |
| Mediate Knowledge | Knowledge gained through inference from other knowledge |
| Immediate Knowledge | Knowledge gained directly through perception or intuition |
| Term | The word or group of words used as subject or predicate of a proposition |
| Proposition | A declarative sentence which is either true or false |
| Inference | The mental process of drawing a conclusion from premises |
| Argument | A group of propositions in which one (the conclusion) is claimed to follow from others (premises) |
| Validity | The property of an argument whose conclusion necessarily follows from its premises |
| Truth | The agreement of a proposition with reality |
| Formal Truth | Self-consistency of thought, independent of facts |
| Material Truth | Correspondence of thought with the actual world |
| Deduction | Inference from general to particular; conclusion necessarily follows |
| Induction | Inference from particular to general; conclusion is probable |
| Fallacy | An error in reasoning that makes an argument invalid |
| Symbolic Logic | Modern Logic which uses artificial symbols and mathematical methods |
| Ideogram | A symbol that directly represents an idea or concept |
| Laws of Thought | The principles of Identity, Contradiction and Excluded Middle |
Key Comparison Tables
Truth vs Validity
| Point | Truth | Validity |
|---|---|---|
| Belongs to | Propositions | Arguments |
| Test | Agreement with facts | Necessary connection between premises and conclusion |
| Concerned with | Matter / content | Form / structure |
| Example | “Snow is white” — true | “All A is B; All B is C; therefore All A is C” — valid |
Deductive vs Inductive Inference
| Point | Deductive | Inductive |
|---|---|---|
| Direction | General to particular | Particular to general |
| Conclusion | Necessarily follows | Probable; may go beyond premises |
| Information | No new factual content | Adds new factual generalisation |
| Truth concerned | Formal truth (validity) | Material truth (factual) |
| Example | All men are mortal; Socrates is a man; therefore Socrates is mortal | This crow is black, that crow is black, … therefore all crows are black |
Logic vs Psychology vs Grammar vs Mathematics
| Point | Logic | Psychology | Grammar | Mathematics |
|---|---|---|---|---|
| Nature | Normative | Positive | Normative | Formal / Deductive |
| Subject matter | Valid reasoning | Mental processes as facts | Correct use of language | Quantity, number, magnitude |
| Standard | Truth | Description of behaviour | Linguistic correctness | Quantitative exactness |
| Method | Inferential | Observational, experimental | Rule-based | Deductive and symbolic |
| Universality | Universal | Universal | Language-specific | Universal |
Major Definitions of Logic by Philosophers
| Philosopher | Definition of Logic |
|---|---|
| Aristotle | The instrument (Organon) of all sciences; the science of demonstration |
| J. S. Mill | “The science of the operations of the understanding which are subservient to the estimation of evidence” |
| Richard Whately | “The science as well as the art of reasoning” |
| Alexander Bain | “The science of proof or evidence” |
| H. W. B. Joseph | “The science which studies the general principles in accordance with which we think about real things” |
| L. S. Stebbing | “The science which investigates the general principles of valid thought” |
| Cohen and Nagel | “The science of the most general laws of valid inference” |
| Creighton | “Logic is a science of thought as thought” |
Important Long Answer Questions (Extended)
Q7. Explain the etymological meaning of “Logic” and discuss the various definitions given by different philosophers.
Answer: The English word “Logic” is derived from the Greek term “Logos”. The word “Logos” carries multiple meanings — “word”, “speech”, “reason”, “discourse” and most importantly “thought as expressed in language”. Therefore, etymologically Logic is the science that deals with thought as it finds expression in language. Yet not every thought concerns the logician; only that organised thought which appears in the form of inference forms its subject matter.
Different philosophers have offered different definitions of Logic, each highlighting a particular aspect:
(i) Aristotle considered Logic to be the Organon — the instrument or tool of all sciences. For him, Logic was the universal method of demonstration that every other science had to follow.
(ii) John Stuart Mill defined it as “the science of the operations of the understanding which are subservient to the estimation of evidence”. Mill’s definition makes clear that Logic concerns itself with how we weigh evidence to arrive at truth.
(iii) Richard Whately, an English logician, called Logic “the science as well as the art of reasoning”, thereby acknowledging both its theoretical and practical aspects.
(iv) Alexander Bain regarded Logic as “the science of proof or evidence”, emphasising that Logic deals with how a statement is rationally established.
(v) H. W. B. Joseph defined it as “the science which studies the general principles in accordance with which we think about real things”, emphasising the relation of Logic to reality.
(vi) L. Susan Stebbing wrote that Logic is “the science which investigates the general principles of valid thought”.
(vii) M. R. Cohen and Ernest Nagel, in their famous textbook, defined Logic as “the science of the most general laws of valid inference”. This is regarded as one of the most accurate modern definitions.
(viii) Creighton simply called Logic “the science of thought as thought”. Taking all these definitions together, we may say: Logic is the normative science which investigates the general principles of valid inference, dealing with thought as expressed in language.
Q8. State the characteristics of Modern (Symbolic) Logic.
Answer: Modern Symbolic Logic, developed largely in the late 19th and early 20th centuries by George Boole, Gottlob Frege, Giuseppe Peano, Bertrand Russell and Alfred North Whitehead, has the following salient characteristics:
(i) Use of artificial symbols: Instead of ordinary words, Modern Logic employs precise symbols (p, q, r for propositions; ~, ·, ∨, ⊃, ≡ for connectives) which avoid the ambiguity of natural language.
(ii) Greater exactness: Because symbols have fixed meanings, the reasoning becomes mathematically exact and unambiguous.
(iii) Wide scope: It encompasses propositional logic, predicate logic, the logic of relations and the logic of classes — far broader than the traditional syllogism.
(iv) Calculative method: Inferences are drawn by applying definite rules of transformation, almost like algebraic operations. Hence Modern Logic is sometimes called “logical calculus”.
(v) Generality: Modern Logic is not tied to any subject matter; its rules apply universally to any domain of valid reasoning.
(vi) Close link with Mathematics: Russell and Whitehead’s Principia Mathematica showed that mathematics itself can be derived from logical principles.
(vii) Use of formal systems: It develops complete formal systems with axioms, rules of inference and theorems, allowing mechanical proof-checking. These features make Modern Logic the most powerful and rigorous instrument of reasoning yet developed.
Q9. Why is Logic regarded as a science of sciences? Discuss.
Answer: Logic is sometimes called the “science of sciences” because every other science depends on it for its method. Each science makes use of definitions, classifications, hypotheses and inferences — but the principles governing these are studied not by any particular science but by Logic. Whether the subject matter is Physics or Botany, Economics or History, the reasoning involved must conform to logical laws if the conclusions are to be valid. Aristotle therefore called Logic the Organon, meaning the instrument or tool of all sciences. Logic does not provide the matter of any other science but supplies the universal form within which all knowledge must be cast. Without Logic, no science could test the validity of its theories or distinguish between sound and unsound arguments. In this sense, Logic is foundational to the entire structure of knowledge and rightly deserves the title of the “science of sciences”.
Q10. Discuss the difference between Science and Art with reference to Logic.
Answer: A science is a body of systematised knowledge about a particular subject matter. It is theoretical, concerned with the discovery of truth and the formulation of general laws. An art, on the other hand, is the practical application of knowledge to achieve a definite purpose. It teaches the rules of doing something correctly. The chief differences are:
| Point | Science | Art |
|---|---|---|
| Aim | Knowledge of truth (Theoretical) | Practical doing (Practical) |
| Concerned with | Causes and laws | Means and rules |
| Question asked | Why? What? | How? |
| Result | Body of organised knowledge | Skill or proficiency |
Logic is both a science and an art. It is a science because it organises the principles of valid reasoning; it is an art because it teaches us how to apply these principles when we actually argue. As Whately put it, “Logic is the science as well as the art of reasoning.” Hence the same discipline performs both roles.
Q11. Discuss the difference between a Positive Science and a Normative Science.
Answer: A Positive Science describes facts as they are. It studies actual phenomena, classifies them, and arrives at general laws by observation and experiment. Examples include Physics, Chemistry, Biology, Geology and Psychology. Their concern is the “is” — what actually exists.
A Normative Science, on the other hand, deals with ideals, standards or norms. It does not describe what is, but prescribes what ought to be. Examples include Logic (norm of Truth), Ethics (norm of Goodness) and Aesthetics (norm of Beauty). Logic is normative because it does not describe how people actually think (which is the work of Psychology), but lays down rules of how they ought to think to attain truth.
| Point | Positive Science | Normative Science |
|---|---|---|
| Concerned with | Facts as they are | Ideals — what ought to be |
| Method | Description, observation, experiment | Standard-setting, evaluation |
| Examples | Physics, Chemistry, Biology | Logic, Ethics, Aesthetics |
| Question | What is? | What should be? |
Quick Revision Notes
1. Etymology: Logic ← Greek “Logos” = thought / word / reason.
2. Father of Logic: Aristotle (Organon).
3. Father of Symbolic Logic: G. W. Leibnitz (later developed by Boole, Frege, Russell-Whitehead).
4. Famous Definitions: Mill, Whately, Bain, Joseph, Stebbing, Cohen-Nagel, Creighton.
5. Nature: (a) deals with mediate knowledge; (b) concerned with formal & material truth; (c) science + art; (d) normative.
6. Subject Matter: Term, Proposition, Inference.
7. Laws of Thought: Identity (A is A), Contradiction (A is not non-A), Excluded Middle (A is either B or not B).
8. Two main divisions: Deductive Logic and Inductive Logic.
9. Two main forms historically: Traditional (Aristotelian) and Modern (Symbolic).
10. Ideal of Logic: Truth.
11. Utility: Cultivates clear thinking; detects fallacies; removes prejudice; foundation of all sciences; practical aid in law, debate, daily life.
12. Truth vs Validity: Truth → propositions (matter); Validity → arguments (form).
This complete chapter solution has been prepared exclusively for the ASSEB (Assam State School Education Board) Class 11 Higher Secondary First Year syllabus, English Medium, by HSLC Guru. For more chapters, visit hslcguru.com.