Metamath Proof Explorer

Theorem sstr

Description: Transitivity of subclass relationship. Theorem 6 of Suppes p. 23. (Contributed by NM, 5-Sep-2003)

Ref Expression
Assertion sstr A B B C A C


Step Hyp Ref Expression
1 sstr2 A B B C A C
2 1 imp A B B C A C