Theorem 19.8w

Weak version of 19.8a and instance of 19.2d. (Contributed by NM, 1-Aug-2017.) (Proof shortened by Wolf Lammen, 4-Dec-2017.)

Hypothesis
19.8w.1
\( \vdash \varphi \rightarrow \forall x \, \varphi \)
Conclusion
\( \vdash \varphi \rightarrow \exists x \, \varphi \)
Proof
19.8w.1
19.2d _