Constructing the Categorical Converter - 2|
We suppose that our Square of Opposition follows the standard SP model (so, for example, the proposition in the upper left corner is All S are P).
SP propositions are related by the rule of Conversion to PS propositions. Moreover, it is possible to construct a second Square for PS propositions.
The image is constructed in two stages. First, we add the PS Square and draw lines to represent straightforward conversions among I and O propositions (upper diagram, right).
Then we add the more complex conversions between A and I propositions (lower diagram, right). Note that these are limited case conversions, being equivalent to the combination of a Subalternation and Conversion.
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10 August 1996