let p, q, r be Element of CQC-WFF ; :: thesis: for X being Subset of CQC-WFF st X |- p => (q => r) holds
X |- q => (p => r)
let X be Subset of CQC-WFF; :: thesis: ( X |- p => (q => r) implies X |- q => (p => r) )
assume A1: X |- p => (q => r) ; :: thesis: X |- q => (p => r)
X |- (p => (q => r)) => (q => (p => r)) by CQC_THE1:98;
hence X |- q => (p => r) by A1, CQC_THE1:92; :: thesis: verum