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Leonardi.DB
a logical geometry project

The Square of Opposition: Past, Present, and Future (2022), p. 5
by Beziau, Jean-Yves; Vandoulakis, Ioannis M.

Caption

Octagon of opposition generalizing Blanché’s hexagon. (Photos courtesy of Jean-Yves Beziau)

Logic

Number of labels per vertex (at most)
1
Errors in the diagram
No

Geometry

Shape
Octagon (regular)
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
none

Edge description

Contains definitions of relations
No
Form
solid lines
,
none
Has arrowheads
No
Overlap
No
Curved
Yes
Hooked
No
As wide as vertices
No
Contains text
No
Label type
none

Style

Diagram is colored
Yes
Diagram is embellished
No
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