let p, q be ZF-formula; :: thesis: for x, y, z, s, t being Variable st All (x,y,z,p) = All (t,s,q) holds
( x = t & y = s & All (z,p) = q )
let x, y, z, s, t be Variable; :: thesis: ( All (x,y,z,p) = All (t,s,q) implies ( x = t & y = s & All (z,p) = q ) )
All (x,y,z,p) = All (x,y,(All (z,p))) ;
hence ( All (x,y,z,p) = All (t,s,q) implies ( x = t & y = s & All (z,p) = q ) ) by Th14; :: thesis: verum