Difference between revisions of "Deduction"
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| − | A '''deduction''' in [[formal logic]] is a conclusion drawn from premises or facts. Such a deduction is said to "follow" from previously stated propositions via certain logical rules | + | A '''deduction''' in [[formal logic]] is a conclusion drawn from premises or facts. Such a deduction is said to "follow" from previously stated propositions via certain logical rules. |
The most famous rule goes as follows: | The most famous rule goes as follows: | ||
Revision as of 23:48, November 2, 2007
A deduction in formal logic is a conclusion drawn from premises or facts. Such a deduction is said to "follow" from previously stated propositions via certain logical rules.
The most famous rule goes as follows:
- A is true.
- If A is true, then B is true.
- Therefore, B is true.
A lesser know rule is:
- If Q is true, then R is true.
- R is not true.
- Therefore, Q is not true.
Aristotle codified the rules of deduction two millenia ago in Ancient Greece. He also added 256 rules about groups of things. For example:
- All men are mortal.
- Socrates as a man.
- Therefore, Socrates is mortal.