Although lack of unity may arise a posteriori as well as a priori, it should be remembered that lack of unity is not a ground of revocation in later proceedings. Therefore, although the objection should certainly be made and amendment insisted upon in clear cases, it should neither be raised nor persisted in on the basis of a narrow, literal or academic approach. This is particularly so where the possible lack of unity does not necessitate a further search. There should be a broad, practical consideration of the degree of interdependence of the alternatives presented, in relation to the state of the art as revealed by the search report. If the common matter of the independent claims is well-known, and the remaining subject-matter of each claim differs from that of the others without there being any unifying novel concept common to all, then clearly there is lack of unity. If, on the other hand, there is a common concept or principle which is novel and inventive, then objection of lack of unity does not arise. For determining what is allowable between these two extremes, rigid rules cannot be given and each case should be considered on its merits, the benefit of any doubt being given to the applicant. For the particular case of claims for a known substance for a number of distinct medical uses, see G‑II, 4.2.
When there is lack of unity, the claimed subject-matter is divided among the separate inventions. In this context the word "invention" means an invention having technical character and concerned with a technical problem within the meaning of Art. 52(1) (see G‑I, 1 and G-I, 2), which does not necessarily need to meet other requirements for patentability, such as novelty and inventive step (see G‑VI and G‑VII).