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

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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