Description: An ordinal number is a subset of On . (Contributed by NM, 11-Aug-1994)
Ref | Expression | ||
---|---|---|---|
Hypothesis | onssi.1 | ⊢ 𝐴 ∈ On | |
Assertion | onssi | ⊢ 𝐴 ⊆ On |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | onssi.1 | ⊢ 𝐴 ∈ On | |
2 | onss | ⊢ ( 𝐴 ∈ On → 𝐴 ⊆ On ) | |
3 | 1 2 | ax-mp | ⊢ 𝐴 ⊆ On |