6
Rank-k m-Types
•For m ¸ 0, there are only finitely many formulas up to logical equivalence over m variables x1, …, xm in FO[0]   [why ?]
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•For m ¸ 0, there are only finitely many formulas up to logical equivalence over m variables x1, …, xm in FO[k+1]   [why ?]