let q, r be Element of CQC-WFF ; :: thesis: (q => (q => r)) => (q => r) in TAUT
( (q => r) => (q => r) in TAUT & ((q => r) => (q => r)) => ((q => (q => r)) => (q => r)) in TAUT ) by Lm18, Th4;
hence (q => (q => r)) => (q => r) in TAUT by CQC_THE1:82; :: thesis: verum