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Leonardi.DB
a logical geometry project

The Modal Equivalence Rules of the Port-Royal Logic (2017), p. 217
by Grey, John

Copyright according to our policy

Caption

A common medieval square of modal opposition

Logic

Aristotelian family
Classical Sigma-2
Boolean complexity
3
Number of labels per vertex (at most)
4
Equivalence between (some) labels of the same vertex
Yes
Analogy between (some) labels of the same vertex
No
Uniqueness of the vertices up to logical equivalence
Yes
Errors in the diagram
No

Geometry

Shape
Rectangle (irregular)
Colinearity range
0
Coplanarity range
0
Cospatiality range
0
Representation of contradiction
By central symmetry

Vertex description

Conceptual info
No
Mnemonic support (AEIO, purpurea ...)
No

Edge description

Style

Diagram is colored
No
Diagram is embellished
No
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