17
Definability of Types
•The number of FOk types is infinite (since no restriction on quantifier depth)
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•Each FOk type is definable as Çi 2 I fi,  where each fi 2 FOk.  However:
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•Theorem. Every FOk type t is defined in FOk.  I.e. there exists ft(x) s.t.
   TpFOk(A, a) = t , A ² ft(a)
•Proof: next time.  For now assume it holds