6 For most of the subsequent discussion, k will be treated as a stock of disembodied
knowledge, i.e., knowledge in books. This is merely an expositional convenience and is
not essential. For example, if one wants to assume that all knowledge is embodied in
some kind of tangible capital such as conventional physical capital or human capital, k
can be reinterpreted throughout as a composite good made up of both knowledge and
the tangible capital good.