take [:(QC-WFF A),(vSUB A):] ; :: thesis: ( [:(QC-WFF A),(vSUB A):] is A -Sub-closed & not [:(QC-WFF A),(vSUB A):] is empty )
( [:(QC-WFF A),(vSUB A):] is Subset of [:([:NAT,(QC-symbols A):] *),(vSUB A):] & ( for k being Nat
for p being QC-pred_symbol of k,A
for ll being QC-variable_list of k,A
for e being Element of vSUB A holds [(<*p*> ^ ll),e] in [:(QC-WFF A),(vSUB A):] ) & ( for e being Element of vSUB A holds [<*[0,0]*>,e] in [:(QC-WFF A),(vSUB A):] ) & ( for p being FinSequence of [:NAT,(QC-symbols A):]
for e being Element of vSUB A st [p,e] in [:(QC-WFF A),(vSUB A):] holds
[(<*[1,0]*> ^ p),e] in [:(QC-WFF A),(vSUB A):] ) & ( for p, q being FinSequence of [:NAT,(QC-symbols A):]
for e being Element of vSUB A st [p,e] in [:(QC-WFF A),(vSUB A):] & [q,e] in [:(QC-WFF A),(vSUB A):] holds
[((<*[2,0]*> ^ p) ^ q),e] in [:(QC-WFF A),(vSUB A):] ) & ( for x being bound_QC-variable of A
for p being FinSequence of [:NAT,(QC-symbols A):]
for e being Element of vSUB A st [p,((QSub A) . [((<*[3,0]*> ^ <*x*>) ^ p),e])] in [:(QC-WFF A),(vSUB A):] holds
[((<*[3,0]*> ^ <*x*>) ^ p),e] in [:(QC-WFF A),(vSUB A):] ) ) by Th7;
hence ( [:(QC-WFF A),(vSUB A):] is A -Sub-closed & not [:(QC-WFF A),(vSUB A):] is empty ) ; :: thesis: verum