Things That are Right with the Traditional Square of Opposition (2008), p. 4
by Parsons, Terence

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Logic

Aristotelian family

Classical Sigma-2

Boolean complexity

3

Number of labels per vertex (at most)

1

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

Form

none

Label type

linguistic

Language

English

Lexical field

syllogistics

Contains partial sentences or single words

No

Contains abbreviations

Yes

Edge description

Style

Diagram is colored

No

Diagram is embellished

No

Additional notes

This diagram only visualizes the relations that are explicitly discussed in Aristotle's Peri Hermeneias, viz., contradiction and contrariety. The relations of subcontrariety and subalternation can be derived from this.