let Al be QC-alphabet ; :: thesis: for p being Element of CQC-WFF Al
for x being bound_QC-variable of Al holds (All (x,p)) => p is valid
let p be Element of CQC-WFF Al; :: thesis: for x being bound_QC-variable of Al holds (All (x,p)) => p is valid
let x be bound_QC-variable of Al; :: thesis: (All (x,p)) => p is valid
(All (x,p)) => p in TAUT Al by Th12;
hence (All (x,p)) => p is valid by Lm13; :: thesis: verum