Although lack of unity may arise a posteriori as well as a priori, it should be remembered that lack Lack of unity is not a ground of revocation in later proceedings. Therefore, although the objection is should certainly be made and amendment insisted upon in clear cases, it is should neither be raised nor persisted ininsisted upon 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 a lack of unity is established, the claimed subject-matter is divided among the separate inventions is divided into separate inventions and/or inventions grouped together in view of their technical relationships, i.e. according to any common matter comprising same or corresponding special technical features. In this context the word "invention" means, an invention must have having technical character and be concerned with a technical problem within the meaning of Art. 52(1) (see G‑I, 1 and G-I, 2), which but it does not necessarily need to meet other requirements for patentability, such as novelty and inventive step (see G‑VI and G‑VII).
Lack of unity may be evident a priori, i.e. prior to carrying out a prior-art search, the lack of unity being based on the content of the patent application in suit and common general knowledge of the skilled person.
Lack of unity may also become apparent a posteriori, i.e. after taking into account also the relevance of the prior art revealed by the search in terms of novelty and inventive step.