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UGC NET PAPER 1 · UNIT 05 · MODULE 2: REASONING, SERIES, CODES AND RELATIONS · TOPIC 1

Types of Reasoning

Deductive versus inductive, abductive and analogical reasoning, with a quick way to identify the type in an MCQ.

  • 9 sub-topics
  • 5 min read
  • Topic 1 of 17

What this topic covers

9 sub-topics, in the order to study them. Tap one to jump to it.

  1. §OverviewReasoning is the mental process of moving from known statements (premises) to a new statement (conclusion), and the whole chain together is called an argument.
  2. 1.1Basic vocabulary (frequently asked as memory questions)Covers Premise, Conclusion, Valid argument, Sound argument, Strong or weak argument and more.
    • Premise
    • Conclusion
    • Valid argument
    • Sound argument
    • Strong or weak argument
  3. 1.2Deductive reasoningMeaning.
    • Meaning
    • Key features
    • necessity
    • valid or invalid
    • Aristotle
  4. 1.3Inductive reasoningMeaning.
    • Meaning
    • probable
    • Key features
    • strong or weak
    • Francis Bacon
  5. 1.4Abductive reasoningCovers inference to the best explanation.
    • C. S. Peirce
  6. 1.5Analogical reasoningIt compares two cases that share several features and concludes that a further feature of one also belongs to the other. Strength depends on how many relevant similarities…
  7. 1.6Other types you may meetCovers Hypothetico-deductive reasoning, Critical reasoning, Verbal reasoning, Non-verbal reasoning, Mathematical or numerical reasoning and more.
    • Critical reasoning
    • Verbal reasoning
    • Non-verbal reasoning
    • Causal reasoning
  8. 1.7Deductive versus inductive at a glancePoint Deductive Inductive Direction General to particular Particular to general Conclusion Certain if premises true and form valid Only probable New information None beyond…
  9. 1.8Tricks to identify the type in an MCQCovers Direction test, Certainty test, Keyword test, Best-explanation test.
    • Direction test
    • Certainty test
    • Keyword test
    • Best-explanation test
  10. 1.9Common trapsSaying a valid argument must have a true conclusion. It does not. Calling an inductive argument "valid" or "invalid". Use strong or weak. Confusing the direction. Deductive…

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§Overview#

Reasoning is the mental process of moving from known statements (premises) to a new statement (conclusion), and the whole chain together is called an argument. The type of reasoning depends on how strongly the premises support the conclusion and in which direction the argument travels.

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1.1Basic vocabulary (frequently asked as memory questions)#

In brief

Covers Premise, Conclusion, Valid argument, Sound argument, Strong or weak argument and more.

  • Premise
  • Conclusion
  • Valid argument
  • Sound argument
  • Strong or weak argument
  • Truth and falsity
  • validity and invalidity

  • Premise: a statement offered as a reason or evidence.

  • Conclusion: the statement that is claimed to follow from the premises.

  • Valid argument: a deductive argument in which the conclusion cannot be false if the premises are true. Validity concerns the form of the argument, not the truth of its statements.

  • Sound argument: a valid argument whose premises are actually true.

  • Strong or weak argument: terms used for inductive arguments, where the premises make the conclusion more or less probable.

  • Truth and falsity apply to statements; validity and invalidity apply to deductive arguments. This difference is a favourite MCQ trap.

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1.2Deductive reasoning#

In brief

Meaning.

  • Meaning
  • Key features
  • necessity
  • valid or invalid
  • Aristotle
  • Examples
  • Remember

Meaning. It moves from the general to the particular. If the premises are true and the form is valid, the conclusion is certain.

Key features

  • The conclusion is already contained in the premises, so it gives no new information beyond them.

  • The conclusion follows with necessity (certainty).

  • Judged as valid or invalid.

  • Associated with Aristotle and the syllogism.

  • Mathematics and formal logic are deductive.

Examples

  • All teachers are graduates. Meena is a teacher. Therefore Meena is a graduate.

  • All metals conduct electricity. Copper is a metal. Therefore copper conducts electricity.

Remember: a deductive argument can be valid yet have a false conclusion if a premise is false (All birds can swim; a crow is a bird; so a crow can swim is valid but unsound).

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1.3Inductive reasoning#

In brief

Meaning.

  • Meaning
  • probable
  • Key features
  • strong or weak
  • Francis Bacon
  • Examples
  • Kinds of induction
  • Enumerative induction

Meaning. It moves from particular observations to a general conclusion. The conclusion goes beyond the premises, so it is only probable, never certain.

Key features

  • The conclusion adds new information, so it can be false even when all premises are true.

  • Judged as strong or weak, not valid or invalid.

  • A single counter-example can break an inductive generalisation.

  • Associated with Francis Bacon and the scientific method of observation (Novum Organum).

  • More supporting cases and more varied cases make the argument stronger.

Examples

  • The sun has risen every day in recorded history, so it will rise tomorrow.

  • Every crow I have seen is black, so all crows are black.

Kinds of induction

  • Enumerative induction: generalising from a count of instances.

  • Statistical generalisation: from a sample to a population (a survey of 1,000 voters predicts a result).

  • Analogical induction: reasoning from similarity (see 2.4).

  • Causal inference: finding causes. John Stuart Mill gave five methods: agreement, difference, joint method of agreement and difference, residues, and concomitant variations.

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1.4Abductive reasoning#

In brief

Covers inference to the best explanation.

  • C. S. Peirce

  • Also called inference to the best explanation and associated with C. S. Peirce.

  • You observe a surprising fact and propose the most likely explanation. Example: the road is wet, so it probably rained.

  • Doctors reasoning from symptoms to the most likely disease, and detectives, use abduction.

  • Like induction, its conclusion is only probable.

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1.5Analogical reasoning#

In brief

It compares two cases that share several features and concludes that a further feature of one also belongs to the other. Strength depends on how many relevant similarities…

  • It compares two cases that share several features and concludes that a further feature of one also belongs to the other.

  • Strength depends on how many relevant similarities exist and whether any relevant difference exists.

  • Example: Medicine X was safe on mice and mice share many traits with humans, so it may be safe for humans.

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1.6Other types you may meet#

In brief

Covers Hypothetico-deductive reasoning, Critical reasoning, Verbal reasoning, Non-verbal reasoning, Mathematical or numerical reasoning and more.

  • Critical reasoning
  • Verbal reasoning
  • Non-verbal reasoning
  • Causal reasoning

  • Hypothetico-deductive reasoning: form a hypothesis, deduce its consequences, then test them. This is how most science works and it combines induction and deduction.

  • Critical reasoning: evaluating whether an argument is strong, whether assumptions are hidden and whether evidence is relevant.

  • Verbal reasoning: problems stated in words (syllogisms, statements and conclusions).

  • Non-verbal reasoning: problems based on figures, patterns and diagrams.

  • Mathematical or numerical reasoning: series, coding, relations and arithmetic, which is the rest of this unit.

  • Causal reasoning: arguing that one event produces another.

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1.7Deductive versus inductive at a glance#

In brief

Point Deductive Inductive Direction General to particular Particular to general Conclusion Certain if premises true and form valid Only probable New information None beyond…

Point Deductive Inductive
Direction General to particular Particular to general
Conclusion Certain if premises true and form valid Only probable
New information None beyond the premises Yes, goes beyond the premises
Judged as Valid or invalid Strong or weak
Effect of an extra premise Cannot weaken a valid argument Can strengthen or weaken it
Typical field Mathematics, formal logic Natural and social science, daily life
Linked thinker Aristotle Francis Bacon, J. S. Mill

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1.8Tricks to identify the type in an MCQ#

In brief

Covers Direction test, Certainty test, Keyword test, Best-explanation test.

  • Direction test
  • Certainty test
  • Keyword test
  • Best-explanation test

  1. Direction test: general rule to specific case is deductive; specific cases to a rule is inductive.

  2. Certainty test: ask whether the conclusion could still be false while every premise is true. If it cannot, the argument is deductive; if it can, it is inductive.

  3. Keyword test: "all, every, therefore necessarily" point to deduction; "most, so far, probably, in every case observed" point to induction.

  4. Best-explanation test: if the conclusion explains an observed fact, think abduction.

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1.9Common traps#

In brief

Saying a valid argument must have a true conclusion. It does not. Calling an inductive argument "valid" or "invalid". Use strong or weak. Confusing the direction. Deductive…

  • Saying a valid argument must have a true conclusion. It does not.

  • Calling an inductive argument "valid" or "invalid". Use strong or weak.

  • Confusing the direction. Deductive is not "specific to general".

  • Assuming that a conclusion drawn from true premises is automatically deductive.

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Test yourself on Types of Reasoning

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↑ Module 2: Reasoning, Series, Codes and Relations · All 18 topics in Mathematical Reasoning · Unit overview and sample MCQs

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