let A be QC-alphabet ; :: thesis: for q, r being Element of CQC-WFF A st q => (q => r) is valid holds
q => r is valid
let q, r be Element of CQC-WFF A; :: thesis: ( q => (q => r) is valid implies q => r is valid )
assume A1: q => (q => r) is valid ; :: thesis: q => r is valid
(q => (q => r)) => (q => r) is valid ;
hence q => r is valid by A1, CQC_THE1:65; :: thesis: verum