:: deftheorem Def14 defines IPC_theory INTPRO_1:def 14 :
for T being Subset of MC-wff holds
( T is IPC_theory iff for p, q, r being Element of MC-wff holds
( p => (q => p) in T & (p => (q => r)) => ((p => q) => (p => r)) in T & (p '&' q) => p in T & (p '&' q) => q in T & p => (q => (p '&' q)) in T & p => (p 'or' q) in T & q => (p 'or' q) in T & (p => r) => ((q => r) => ((p 'or' q) => r)) in T & FALSUM => p in T & ( p in T & p => q in T implies q in T ) ) );