let p be Element of CQC-WFF ; :: thesis: for x being bound_QC-variable st p is valid holds
Ex (x,p) is valid
let x be bound_QC-variable; :: thesis: ( p is valid implies Ex (x,p) is valid )
assume A1: p is valid ; :: thesis: Ex (x,p) is valid
p => (Ex (x,p)) is valid by Th18;
hence Ex (x,p) is valid by A1, CQC_THE1:65; :: thesis: verum