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_THE1:104; :: thesis: verum