Single Idea 9675

[catalogued under 4. Formal Logic / F. Set Theory ST / 2. Mechanics of Set Theory / a. Symbols of ST]

Full Idea

a ∈ X means that a is a member of the set X, that is, a is one of the objects in X. a ∉ X indicates that a is not in X.

Gist of Idea

a ∈ X says a is an object in set X; a ∉ X says a is not in X

Source

Graham Priest (Intro to Non-Classical Logic (1st ed) [2001], 0.1.2)

Book Reference

Priest,Graham: 'Introduction to Non-Classical Logic' [CUP 2001], p.-7

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