let A be QC-alphabet ; :: thesis: for p, q, r, s being Element of CQC-WFF A holds ((q => r) => p) => ((q => s) => ((s => p) => p)) in TAUT A
let p, q, r, s be Element of CQC-WFF A; :: thesis: ((q => r) => p) => ((q => s) => ((s => p) => p)) in TAUT A
( (q => s) => (((q => r) => p) => ((s => p) => p)) in TAUT A & ((q => s) => (((q => r) => p) => ((s => p) => p))) => (((q => r) => p) => ((q => s) => ((s => p) => p))) in TAUT A ) by Lm19, Th8;
hence ((q => r) => p) => ((q => s) => ((s => p) => p)) in TAUT A by CQC_THE1:46; :: thesis: verum