paragraph 230 in volume 2, chapter 13, Matters of Jurisdiction
The distinction between a preliminary objection, especially to the admissibility, and a defence to the merits, is also subtle. As a rough rule of thumb, it is probable that when the facts and arguments in support of the objection are substantially the same as the facts and arguments on which the merits of the case depend, or when to decide the objection would require decision on what, in the particular case, are substantive as…