let H be ZF-formula; :: thesis: for x being Variable
for M being non empty set st M |= H holds
M |= Ex (x,H)
let x be Variable; :: thesis: for M being non empty set st M |= H holds
M |= Ex (x,H)
let M be non empty set ; :: thesis: ( M |= H implies M |= Ex (x,H) )
assume A1: M |= H ; :: thesis: M |= Ex (x,H)
let v be Function of VAR,M; :: according to ZF_MODEL:def 5 :: thesis: M,v |= Ex (x,H)
M,v / (x,(v . x)) |= H by A1;
hence M,v |= Ex (x,H) by Th73; :: thesis: verum