 The above discussion has included such phrases as “the hybrid of ∧ and ∨”; the totality of principles governing such a connective being those common to ∧ and ∨, we obviously do not have a connective uniquely characterized by those principles—in which case is it legitimate to speak of the hybrid…? I take this way of speaking to be as harmless as speaking of “the ☐ operator of S5”, where again the logical principles involved are insufficient to characterize the connective uniquely—in terms of the Boolean connectives or otherwise—at least if we are Fmla, Set-Fmla or Set-Set, and in the latter cases, working with the so-called local (generalized) consequence  relation.[34]  (See Section  5  for the distinction between the local and the global consequence relations determined by a class of models.) One could say that in the monomodal, unreduplicated case, we have a single connective playing a certain role and we can refer to it in that context as the connective playing the role in question, while conceding, as we learn from the reduplicated case, that this is a role that can be played simultaneously (i.e. in a single logic) by several non-equivalent connectives. This is the kind of situation Łukasiewicz had in mind when, in his (1953), he likened certain pairs of connectives to “twins who cannot be distinguished when met separately, but are instantly recognised as two when seen together”.