Oppositional Square - the device used to represent proposition using their individual symbols (A, E, I, O) to manifest the opposite relationships with other propositions.
KIND OF LOGICAL OPPOSITION
1. Contradictory Opposition - is a kind of opposition that exists between propositions which differ both quality and quantity.
Rules:
a. The two propositions cannot be true or false at the same time.
- If one is true then the other id false at the same time.
2. Contrary Opposition - exists between two propositions which differ also in quality.
Rules:
a. If one is true, the other is false.
b. If one is false, the other is doubtful.
3. Sub-contrary Opposition - exists between two proposition which differ also in quality.
Rules:
a. If one is true, the other is doubtful.
b. if one is false the other is true.
4. Sub-altern Opposition - exist between two proposition which differ from quantity.
Rules:
a. If the universal is true, the particular must be true.
b. If the universal is false, the particular must be doubtful.
c. If the particular is true the universal must be doubtful.
d. If the particular is false, the universal must be false.
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