let p be Element of CQC-WFF ; :: thesis: (p 'or' p) => p in TAUT
( (p 'or' p) => (('not' p) => p) in TAUT & (('not' p) => p) => p in TAUT ) by Th5, CQC_THE1:42;
hence (p 'or' p) => p in TAUT by LUKASI_1:3; :: thesis: verum