let p, r, s, q be Element of CQC-WFF ; :: thesis: p => (((('not' p) => r) => s) => ((q => r) => s)) in TAUT
( (('not' p) => q) => (((('not' p) => r) => s) => ((q => r) => s)) in TAUT & ((('not' p) => q) => (((('not' p) => r) => s) => ((q => r) => s))) => (p => (((('not' p) => r) => s) => ((q => r) => s))) in TAUT ) by Lm3, Lm5;
hence p => (((('not' p) => r) => s) => ((q => r) => s)) in TAUT by CQC_THE1:82; :: thesis: verum