let C be non empty transitive AltCatStr ; for D being full SubCatStr of C st the carrier of D = the carrier of C holds
AltCatStr(# the carrier of D, the Arrows of D, the Comp of D #) = AltCatStr(# the carrier of C, the Arrows of C, the Comp of C #)
let D be full SubCatStr of C; ( the carrier of D = the carrier of C implies AltCatStr(# the carrier of D, the Arrows of D, the Comp of D #) = AltCatStr(# the carrier of C, the Arrows of C, the Comp of C #) )
assume A1:
the carrier of D = the carrier of C
; AltCatStr(# the carrier of D, the Arrows of D, the Comp of D #) = AltCatStr(# the carrier of C, the Arrows of C, the Comp of C #)
the Arrows of D =
the Arrows of C || the carrier of D
by Def13
.=
the Arrows of C
by A1
;
hence
AltCatStr(# the carrier of D, the Arrows of D, the Comp of D #) = AltCatStr(# the carrier of C, the Arrows of C, the Comp of C #)
by A1, Th25; verum