Lambek and Scott demonstrate in Introduction to higher order categorical logic the existence of a parametrized nno when we are in a cartesian closed category (CCC) with a "simple nno" and suggest the possibility of define a parametrized nno in the context of a cartesian category (CC) with a simple nno. In which cases can it be done in the context of a CC? Could it be done only with numerals or (in the more general case of a) strong nno?

Ximo.