let p, r, s, q be Element of CQC-WFF ; :: thesis: ((p => r) => s) => ((p => q) => ((q => r) => s)) in TAUT
( (p => q) => (((p => r) => s) => ((q => r) => s)) in TAUT & ((p => q) => (((p => r) => s) => ((q => r) => s))) => (((p => r) => s) => ((p => q) => ((q => r) => s))) in TAUT ) by Lm3, Th8;
hence ((p => r) => s) => ((p => q) => ((q => r) => s)) in TAUT by CQC_THE1:46; :: thesis: verum