Difference between revisions of "Deduction"

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(that was induction, not deduction.)
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#If A is true, then B is true.
 
#If A is true, then B is true.
 
#Therefore, B is true.
 
#Therefore, B is true.
 
A lesser known 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:
 
Aristotle codified the rules of deduction two millenia ago in [[Ancient Greece]]. He also added 256 rules about groups of things. For example:

Revision as of 01:37, October 30, 2009

A deduction in formal logic is a way of proving a proposition. It is used most often in geometry, but also has its place in philosophy and law. Sadly, it is often left out of ideology and even science.

When a conclusion is inferred from premises or facts, it is said to "follow" from previously stated propositions via certain logical rules.

The most famous rule goes as follows:

  1. A is true.
  2. If A is true, then B is true.
  3. Therefore, B is true.

Aristotle codified the rules of deduction two millenia ago in Ancient Greece. He also added 256 rules about groups of things. For example:

  1. All men are mortal.
  2. Socrates is a man.
  3. Therefore, Socrates is mortal.

See also: