let CX be Consistent Subset of CQC-WFF ; :: thesis: for JH being Henkin_interpretation of CX
for n being Element of NAT st ( for p being Element of CQC-WFF st QuantNbr p <= n & CX is negation_faithful & CX is with_examples holds
( JH, valH |= p iff CX |- p ) ) holds
for p being Element of CQC-WFF st QuantNbr p <= n + 1 & CX is negation_faithful & CX is with_examples holds
( JH, valH |= p iff CX |- p )

let JH be Henkin_interpretation of CX; :: thesis: for n being Element of NAT st ( for p being Element of CQC-WFF st QuantNbr p <= n & CX is negation_faithful & CX is with_examples holds
( JH, valH |= p iff CX |- p ) ) holds
for p being Element of CQC-WFF st QuantNbr p <= n + 1 & CX is negation_faithful & CX is with_examples holds
( JH, valH |= p iff CX |- p )

let n be Element of NAT ; :: thesis: ( ( for p being Element of CQC-WFF st QuantNbr p <= n & CX is negation_faithful & CX is with_examples holds
( JH, valH |= p iff CX |- p ) ) implies for p being Element of CQC-WFF st QuantNbr p <= n + 1 & CX is negation_faithful & CX is with_examples holds
( JH, valH |= p iff CX |- p ) )

assume A1: for p being Element of CQC-WFF st QuantNbr p <= n & CX is negation_faithful & CX is with_examples holds
( JH, valH |= p iff CX |- p ) ; :: thesis: for p being Element of CQC-WFF st QuantNbr p <= n + 1 & CX is negation_faithful & CX is with_examples holds
( JH, valH |= p iff CX |- p )

let p be Element of CQC-WFF ; :: thesis: ( QuantNbr p <= n + 1 & CX is negation_faithful & CX is with_examples implies ( JH, valH |= p iff CX |- p ) )
assume A2: ( QuantNbr p <= n + 1 & CX is negation_faithful & CX is with_examples ) ; :: thesis: ( JH, valH |= p iff CX |- p )
A3: ( QuantNbr p <= n implies ( JH, valH |= p iff CX |- p ) ) by A1, A2;
now
assume A4: QuantNbr p = n + 1 ; :: thesis: ( JH, valH |= p iff CX |- p )
then 1 <= QuantNbr p by NAT_1:11;
then consider q being Element of CQC-WFF such that
A5: ( q is_subformula_of p & QuantNbr q = 1 ) by SUBSTUT2:34;
consider L being PATH of q,p;
A6: ( 1 <= len L & L . 1 = q & L . (len L) = p & ( for k being Element of NAT st 1 <= k & k < len L holds
ex G1, H1 being Element of QC-WFF st
( L . k = G1 & L . (k + 1) = H1 & G1 is_immediate_constituent_of H1 ) ) ) by A5, SUBSTUT2:def 6;
defpred S1[ Element of NAT ] means ( 1 <= $1 & $1 <= len L implies ex p1 being Element of CQC-WFF st
( p1 = L . $1 & QuantNbr q <= QuantNbr p1 & ( CX |- p1 implies JH, valH |= p1 ) & ( JH, valH |= p1 implies CX |- p1 ) ) );
A7: S1[ 0 ] ;
A8: for k being Element of NAT st S1[k] holds
S1[k + 1]
proof
let k be Element of NAT ; :: thesis: ( S1[k] implies S1[k + 1] )
assume A9: S1[k] ; :: thesis: S1[k + 1]
assume A10: ( 1 <= k + 1 & k + 1 <= len L ) ; :: thesis: ex p1 being Element of CQC-WFF st
( p1 = L . (k + 1) & QuantNbr q <= QuantNbr p1 & ( CX |- p1 implies JH, valH |= p1 ) & ( JH, valH |= p1 implies CX |- p1 ) )

set j = k + 1;
A11: now
assume k = 0 ; :: thesis: ex q, p1 being Element of CQC-WFF st
( p1 = L . (k + 1) & QuantNbr q <= QuantNbr p1 & ( CX |- p1 implies JH, valH |= p1 ) & ( JH, valH |= p1 implies CX |- p1 ) )

then A12: L . (k + 1) = q by A5, SUBSTUT2:def 6;
take q = q; :: thesis: ex p1 being Element of CQC-WFF st
( p1 = L . (k + 1) & QuantNbr q <= QuantNbr p1 & ( CX |- p1 implies JH, valH |= p1 ) & ( JH, valH |= p1 implies CX |- p1 ) )

( JH, valH |= q iff CX |- q ) by A2, A5, Th15;
hence ex p1 being Element of CQC-WFF st
( p1 = L . (k + 1) & QuantNbr q <= QuantNbr p1 & ( CX |- p1 implies JH, valH |= p1 ) & ( JH, valH |= p1 implies CX |- p1 ) ) by A12; :: thesis: verum
end;
now
assume k <> 0 ; :: thesis: ex s, p1 being Element of CQC-WFF st
( p1 = L . (k + 1) & QuantNbr q <= QuantNbr p1 & ( CX |- p1 implies JH, valH |= p1 ) & ( JH, valH |= p1 implies CX |- p1 ) )

then ( 0 < k & k < k + 1 ) by NAT_1:3, NAT_1:13;
then A13: ( 0 + 1 <= k & k < len L ) by A10, NAT_1:13;
then consider G1, H1 being Element of QC-WFF such that
A14: ( L . k = G1 & L . (k + 1) = H1 & G1 is_immediate_constituent_of H1 ) by A5, SUBSTUT2:def 6;
consider p1 being Element of CQC-WFF such that
A15: ( QuantNbr q <= QuantNbr p1 & p1 = L . k & ( CX |- p1 implies JH, valH |= p1 ) & ( JH, valH |= p1 implies CX |- p1 ) ) by A9, A13;
consider F3 being QC-formula such that
A16: ( F3 = L . (k + 1) & F3 is_subformula_of p ) by A5, A10, SUBSTUT2:27;
reconsider s = H1 as Element of CQC-WFF by A5, A10, A14, SUBSTUT2:28;
take s = s; :: thesis: ex p1 being Element of CQC-WFF st
( p1 = L . (k + 1) & QuantNbr q <= QuantNbr p1 & ( CX |- p1 implies JH, valH |= p1 ) & ( JH, valH |= p1 implies CX |- p1 ) )

A17: now
assume s = 'not' p1 ; :: thesis: ex p1 being Element of CQC-WFF st
( p1 = L . (k + 1) & QuantNbr q <= QuantNbr p1 & ( CX |- p1 implies JH, valH |= p1 ) & ( JH, valH |= p1 implies CX |- p1 ) )

then ( QuantNbr q <= QuantNbr s & s = L . (k + 1) & ( CX |- s implies JH, valH |= s ) & ( JH, valH |= s implies CX |- s ) ) by A2, A14, A15, Def1, CQC_SIM1:16, HENMODEL:def 3, VALUAT_1:28;
hence ex p1 being Element of CQC-WFF st
( p1 = L . (k + 1) & QuantNbr q <= QuantNbr p1 & ( CX |- p1 implies JH, valH |= p1 ) & ( JH, valH |= p1 implies CX |- p1 ) ) ; :: thesis: verum
end;
A18: QuantNbr s <= n + 1 by A4, A14, A16, SUBSTUT2:30;
A19: now
given F1 being QC-formula such that A20: s = p1 '&' F1 ; :: thesis: ex p1 being Element of CQC-WFF st
( p1 = L . (k + 1) & QuantNbr q <= QuantNbr p1 & ( CX |- p1 implies JH, valH |= p1 ) & ( JH, valH |= p1 implies CX |- p1 ) )

reconsider F1 = F1 as Element of CQC-WFF by A20, CQC_LANG:19;
A21: QuantNbr s = (QuantNbr p1) + (QuantNbr F1) by A20, CQC_SIM1:17;
then 1 + (QuantNbr F1) <= QuantNbr s by A5, A15, XREAL_1:8;
then 1 + (QuantNbr F1) <= n + 1 by A18, XXREAL_0:2;
then ((QuantNbr F1) + 1) + (- 1) <= (n + 1) + (- 1) by XREAL_1:8;
then ( CX |- F1 iff JH, valH |= F1 ) by A1, A2;
then A22: ( s = L . (k + 1) & ( CX |- s implies JH, valH |= s ) & ( JH, valH |= s implies CX |- s ) ) by A14, A15, A20, Th6, VALUAT_1:29;
QuantNbr p1 <= QuantNbr s by A21, NAT_1:11;
then QuantNbr q <= QuantNbr s by A15, XXREAL_0:2;
hence ex p1 being Element of CQC-WFF st
( p1 = L . (k + 1) & QuantNbr q <= QuantNbr p1 & ( CX |- p1 implies JH, valH |= p1 ) & ( JH, valH |= p1 implies CX |- p1 ) ) by A22; :: thesis: verum
end;
A23: now
given F1 being QC-formula such that A24: s = F1 '&' p1 ; :: thesis: ex p1 being Element of CQC-WFF st
( p1 = L . (k + 1) & QuantNbr q <= QuantNbr p1 & ( CX |- p1 implies JH, valH |= p1 ) & ( JH, valH |= p1 implies CX |- p1 ) )

reconsider F1 = F1 as Element of CQC-WFF by A24, CQC_LANG:19;
A25: QuantNbr s = (QuantNbr p1) + (QuantNbr F1) by A24, CQC_SIM1:17;
then 1 + (QuantNbr F1) <= QuantNbr s by A5, A15, XREAL_1:8;
then 1 + (QuantNbr F1) <= n + 1 by A18, XXREAL_0:2;
then ((QuantNbr F1) + 1) + (- 1) <= (n + 1) + (- 1) by XREAL_1:8;
then ( CX |- F1 iff JH, valH |= F1 ) by A1, A2;
then A26: ( s = L . (k + 1) & ( CX |- s implies JH, valH |= s ) & ( JH, valH |= s implies CX |- s ) ) by A14, A15, A24, Th6, VALUAT_1:29;
QuantNbr p1 <= QuantNbr s by A25, NAT_1:11;
then QuantNbr q <= QuantNbr s by A15, XXREAL_0:2;
hence ex p1 being Element of CQC-WFF st
( p1 = L . (k + 1) & QuantNbr q <= QuantNbr p1 & ( CX |- p1 implies JH, valH |= p1 ) & ( JH, valH |= p1 implies CX |- p1 ) ) by A26; :: thesis: verum
end;
now
given x being bound_QC-variable such that A27: s = All x,p1 ; :: thesis: ex p1 being Element of CQC-WFF st
( p1 = L . (k + 1) & QuantNbr q <= QuantNbr p1 & ( CX |- p1 implies JH, valH |= p1 ) & ( JH, valH |= p1 implies CX |- p1 ) )

A28: QuantNbr s = (QuantNbr p1) + 1 by A27, CQC_SIM1:18;
then QuantNbr p1 < n + 1 by A18, NAT_1:13;
then QuantNbr p1 <= n by NAT_1:13;
then A29: QuantNbr ('not' p1) <= n by CQC_SIM1:16;
A30: QuantNbr q <= QuantNbr s by A15, A28, NAT_1:13;
A31: now
assume JH, valH |= Ex x,('not' p1) ; :: thesis: CX |- Ex x,('not' p1)
then consider y being bound_QC-variable such that
A32: JH, valH |= ('not' p1) . x,y by Th10;
QuantNbr (('not' p1) . x,y) <= n by A29, Th14;
then CX |- ('not' p1) . x,y by A1, A2, A32;
hence CX |- Ex x,('not' p1) by A2, Th3; :: thesis: verum
end;
now
assume CX |- Ex x,('not' p1) ; :: thesis: JH, valH |= Ex x,('not' p1)
then consider y being bound_QC-variable such that
A33: CX |- ('not' p1) . x,y by A2, Th3;
QuantNbr (('not' p1) . x,y) <= n by A29, Th14;
then JH, valH |= ('not' p1) . x,y by A1, A2, A33;
hence JH, valH |= Ex x,('not' p1) by Th10; :: thesis: verum
end;
then ( JH, valH |= 'not' (Ex x,('not' p1)) iff CX |- 'not' (Ex x,('not' p1)) ) by A2, A31, Def1, HENMODEL:def 3, VALUAT_1:28;
then ( s = L . (k + 1) & ( JH, valH |= s implies CX |- s ) & ( CX |- s implies JH, valH |= s ) ) by A14, A27, Th11, Th12;
hence ex p1 being Element of CQC-WFF st
( p1 = L . (k + 1) & QuantNbr q <= QuantNbr p1 & ( CX |- p1 implies JH, valH |= p1 ) & ( JH, valH |= p1 implies CX |- p1 ) ) by A30; :: thesis: verum
end;
hence ex p1 being Element of CQC-WFF st
( p1 = L . (k + 1) & QuantNbr q <= QuantNbr p1 & ( CX |- p1 implies JH, valH |= p1 ) & ( JH, valH |= p1 implies CX |- p1 ) ) by A14, A15, A17, A19, A23, QC_LANG2:def 20; :: thesis: verum
end;
hence ex p1 being Element of CQC-WFF st
( p1 = L . (k + 1) & QuantNbr q <= QuantNbr p1 & ( CX |- p1 implies JH, valH |= p1 ) & ( JH, valH |= p1 implies CX |- p1 ) ) by A11; :: thesis: verum
end;
for k being Element of NAT holds S1[k] from NAT_1:sch 1(A7, A8);
then consider p1 being Element of CQC-WFF such that
A34: ( p1 = L . (len L) & QuantNbr q <= QuantNbr p1 & ( CX |- p1 implies JH, valH |= p1 ) & ( JH, valH |= p1 implies CX |- p1 ) ) by A6;
thus ( JH, valH |= p iff CX |- p ) by A5, A34, SUBSTUT2:def 6; :: thesis: verum
end;
hence ( JH, valH |= p iff CX |- p ) by A2, A3, NAT_1:8; :: thesis: verum