let q, s, p, r be Element of CQC-WFF ; :: thesis: (q => s) => ((s => (p => (q => r))) => (p => (q => r))) in TAUT
( (q => r) => (p => (q => r)) in TAUT & ((q => r) => (p => (q => r))) => ((q => s) => ((s => (p => (q => r))) => (p => (q => r)))) in TAUT ) by Lm20, Th5;
hence (q => s) => ((s => (p => (q => r))) => (p => (q => r))) in TAUT by CQC_THE1:82; :: thesis: verum