let p, q be Element of CQC-WFF ; :: thesis: (p 'or' q) => (q 'or' p) in TAUT
(('not' p) => q) => (('not' q) => p) in TAUT by LUKASI_1:31;
then (p 'or' q) => (('not' q) => p) in TAUT by Lm1;
hence (p 'or' q) => (q 'or' p) in TAUT by Lm1; :: thesis: verum