Description: Inference of abstraction subclass from implication. (Contributed by NM, 31-Mar-1995)
Ref | Expression | ||
---|---|---|---|
Hypothesis | ss2abi.1 | ⊢ ( 𝜑 → 𝜓 ) | |
Assertion | ss2abi | ⊢ { 𝑥 ∣ 𝜑 } ⊆ { 𝑥 ∣ 𝜓 } |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | ss2abi.1 | ⊢ ( 𝜑 → 𝜓 ) | |
2 | ss2ab | ⊢ ( { 𝑥 ∣ 𝜑 } ⊆ { 𝑥 ∣ 𝜓 } ↔ ∀ 𝑥 ( 𝜑 → 𝜓 ) ) | |
3 | 2 1 | mpgbir | ⊢ { 𝑥 ∣ 𝜑 } ⊆ { 𝑥 ∣ 𝜓 } |