Meaning & use
deductive logic
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Meaning
noununcountabletechnical
A way of reasoning in which a conclusion follows with certainty from general statements already accepted as true.
Grammar: Uncountable: deductive logic is used in proofs, not a deductive logic.
Patterns
- deductive logic of something
All birds have feathers and a robin is a bird, so by deductive logic a robin has feathers.
Mathematicians rely on deductive logic to prove theorems.
Detective stories often show deductive logic in action, though real cases need evidence too.
Common combinations
- use deductive logic
- We can use deductive logic to rule out the first two suspects.
- apply deductive logic
- Students apply deductive logic to solve the puzzle.
- by deductive logic
- By deductive logic, the answer must be seven.
- sound deductive logic
- Her argument was built on sound deductive logic.
- basic deductive logic
- Basic deductive logic is taught in introductory philosophy.
Synonyms and how they differ
- deduction
- Deduction names a single act of reasoning from rules to a case, while deductive logic is the whole system.
- formal logic
- Formal logic is a wider field that includes deductive systems, so it is not limited to certain conclusions.
- syllogism
- A syllogism is one specific three-part argument form within deductive logic.
Opposites
Word family
Commonly confused: deductive logic or inductive logic?
deductive logic vs inductive logic
Inductive logic moves from specific observations to a probable general claim, while deductive logic gives certainty when premises are true.
Practice
Which example shows deductive logic?
Choose one answer.
The conclusion follows with certainty from the general rule. The other options reason from patterns or feelings and only reach probable conclusions.
Make it your own
Write a sentence using “deductive logic”, then check it and compare it with the examples above.