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contradictories

The Square of Opposition dates back to the second century of our era (CE) and can be considered as the first mind map, whatever claims Tony Buzan may make. This one is adapted from the page by Terence Parsons on SEP (Stanford Encyclopedia of Philosophy). Parsons, Terence, "The Traditional Square of Opposition", The Stanford Encyclopedia of Philosophy (Fall 2008 Edition), Edward N. Zalta (ed.), URL = .

1. A - Every S is P

   ‘Every S is P’ and ‘Some S is not P’ are contradictories. ‘Every S is P’ and ‘No S is P’ are contraries.

2. I - Some S is P

   ‘Some S is P’ and ‘Some S is not P’ are subcontraries. ‘Some S is P’ is a subaltern of ‘Every S is P’.

3. O - Some S is not P

   ‘Some S is not P’ is a subaltern of ‘No S is P’.

4. E - No S is P

   No S is P’ and ‘Some S is P’ are contradictories.