Theorem exmo

Description: Any proposition holds for some x or holds for at most one x . (Contributed by NM, 8-Mar-1995) Shorten proof and avoid df-eu . (Revised by BJ, 14-Oct-2022)

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

Proof

Step	Hyp	Ref	Expression
1		nexmo	$$⊢\neg \exists x\phi \to {\exists }^{*}x\phi$$
2	1	orri	$$⊢\left(\exists x\phi \vee {\exists }^{*}x\phi \right)$$