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Constructing the Categorical Converter - 2
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).
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10 August 1996 
For Educators Stephen Downes Guide to the Logical Fallacies Copyright © Stephen Downes, 1995-2001 stephen.downes@ualberta.ca |
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).
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.