 The realm of the imaginable includes whatever is epistemically admissible for either logical or epistemic reasons. Neither is purely objective: what can and cannot be imagined seems player-relative, as is being “explicitly” inconsistent (for seeing or overlooking a contradiction is a matter of individual skill). Examples of the imaginable include the existence of a vacuum, infinite velocities, expansions of physical objects, and men being immortal, but not men being  donkeys.[6]  The criteria may be practical: certain hypotheses are not productive. Since the respondent’s goal is to maintain consistency, accepting overtly inconsistent assumptions is a  nonstarter,[7]  and certain impossibilities are such that nobody would agree to defend them even for the sake of  argument.[8]  Defining admissibility in terms of imaginability makes obligationes into a framework for discussing “impossibilities” with applications in  physics[9]  as a science based on conceptual analysis and  thought-experiments,[10]  where the “secundum imaginationem” assumptions play the same role as the modern day idealizations such as mass points or frictionless  movement.[11]