Theorem moor

Description: "At most one" is still the case when a disjunct is removed. (Contributed by NM, 5-Apr-2004)

	Ref	Expression
Assertion	moor	$$⊢{\exists }^{*}x\left(\phi \vee \psi \right)\to {\exists }^{*}x\phi$$

Proof

Step	Hyp	Ref	Expression
1		orc	$$⊢\phi \to \left(\phi \vee \psi \right)$$
2	1	moimi	$$⊢{\exists }^{*}x\left(\phi \vee \psi \right)\to {\exists }^{*}x\phi$$