Metamath Proof Explorer


Theorem mndbn0

Description: The base set of a monoid is not empty. Statement in Lang p. 3. (Contributed by AV, 29-Dec-2023)

Ref Expression
Hypothesis mndbn0.b ⊢ B = Base G
Assertion mndbn0 ⊢ G ∈ Mnd → B ≠ ∅

Proof

Step Hyp Ref Expression
1 mndbn0.b ⊢ B = Base G
2 eqid ⊢ 0 G = 0 G
3 1 2 mndidcl ⊢ G ∈ Mnd → 0 G ∈ B
4 3 ne0d ⊢ G ∈ Mnd → B ≠ ∅