let Al be QC-alphabet ; :: thesis: for p, q being Element of CQC-WFF Al holds p => (('not' p) => q) in TAUT Al
let p, q be Element of CQC-WFF Al; :: thesis: p => (('not' p) => q) in TAUT Al
TAUT Al is being_a_theory by Th11;
hence p => (('not' p) => q) in TAUT Al ; :: thesis: verum