e don't need 3-identity
    because we have 4-identity, 5-identity, 6-identity, ..., in
    the &quot;standard predicate calculus&quot;. The question is not what
    concepts are generated in all the generations that follow the
    establishment of the conceptual resource base (axiom system),
    but what is the minimal set of concepts that we can use to
    generate the needed collection of concepts. And there the
    answer is, in a way that is subject to the usual sorts of
    mathematical proof, that 3-