According to the general theory of law, the use of a tertium comparationis is considered indispensable when comparing distinct legal phenomena, as it provides a shared conceptual foundation that enables coherent and meaningful legal analysis. This methodological assumption presupposes that, despite the diversity of legal systems or normative frameworks, there exists a common element that can serve as a neutral point of reference. However, I seek to challenge this premise by investigating whether, in the context of multi-faith spaces—which are designed to accommodate not only diverse faith practices but also non-believers—such a tertium comparationis can truly be identified. The question arises as to whether these spaces embody any shared normative or conceptual core, or whether their very fluid nature resists the imposition of a unifying analytical category, thereby calling into question the universality of this theoretical legal tool. The consequence of this reasoning is that the very possibility of comparison in this field appears problematic, since in the domain of law and religion it seems difficult to reach an optimal rule. Legal systems differ profoundly from one another, as religious rules. Moreover, believing and non-believing pertain to the innermost sphere of individual conscience.