let p, q, r be Element of CQC-WFF ; :: thesis: ( p => (q => r) in TAUT & p => q in TAUT implies p => r in TAUT )
assume p => (q => r) in TAUT ; :: thesis: ( not p => q in TAUT or p => r in TAUT )
then (p => q) => (p => r) in TAUT by Th19;
hence ( not p => q in TAUT or p => r in TAUT ) by CQC_THE1:46; :: thesis: verum