deduction
dɪ-DUK-shun
/dɪˈdʌk.ʃən/
The action of deducting or subtracting something; or the deriving of a conclusion by reasoning from general premises to a specific instance.
In logic, deduction guarantees the truth of the conclusion if the premises are true, moving from the general to the specific.
The story behind the word. The Latin verb deducere meant 'to lead down' or 'to bring away.' In the realm of logic, to make a deduction is to 'lead your mind down' from a broad, established truth to a specific, inescapable conclusion.
Word relationships
- inference: Inference is a broader term for arriving at a conclusion based on evidence, while deduction is strictly top-down logical reasoning.
- reasoning: Reasoning is the general mental process of thinking, whereas deduction is a specific formal type of logic.
- induction: Induction is reasoning from specific observations to make a general rule, the exact opposite of deduction.
- speculation: Speculation is forming a theory without firm evidence.
Commonly confused with
- induction: Deduction goes from general rules to specific facts; induction goes from specific observations to general rules.
Word family
- deduct (verb): Subtract or take away an amount from a total.
- deductive (adjective): Characterized by or based on the method of deduction.
- deductively (adverb): By process of logical deduction.
Collocations
- logical deduction
- powers of deduction
- tax deduction
Idioms & expressions
- process of deduction
Example sentences
- "It was a simple deduction, yet it served to show the character of the man." Sherlock Holmes explaining his analytical methods. (Arthur Conan Doyle, The Memoirs of Sherlock Holmes, 1892)
Memory hook
When you deduct (subtract) the impossible options, what remains must be the truth (deduction). Sherlock Holmes 'leading down' the clues to find the killer.
When not to use
Do not use when you are just guessing wildly; deduction requires a structured, logical sequence of steps.
Fun facts
- Although Sherlock Holmes is famous for his 'deductions,' most of his reasoning is technically abduction—finding the most likely explanation for a set of observations.
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