It is expedient to give a strictly ‘formal’ and at the same time explicit character to definitions that thus premise, and are premised by, other definitions [...] In the formal definitions of the theory it is not a question of trying to exhaust the intensional nature of the objects or even of delimiting them extensionally on all sides, but only of anchoring them relatively in respect to other objects, similarly defined or premised as basic.
- Hjelmslev (1961), a pag.20-21