 The justification of [R2] is not clearly explained in [RSS]. A minimalist interpretation is that the proposed sentence is implied by [R1] via reductio: If (s) is false, then it is false (trivially); if (s) is not false, it is true, and then it is the case as it signifies, hence it is false. Either way, it is false, hence it is  false.[39]  An obligational explanation is that (s) is regarded as relevant in this casus, and as such can only be conceded or denied. Since its denial implies an inconsistency, such a move must be avoided in a consistency-maintenance game; therefore it should be conceded. Since the casus has been admitted as consistent, it cannot validate an inconsistent move; hence, it must validate its opposite. By the same reasoning, it is possible to deny that (s) is true. Furthermore, Heytesbury refuses to certify the additional meaning of (s) ([RSS] 1494: fol. 6va [1979: 49–50]). Unsatisfactory as this may seem, it is legitimate from the point of view of obligationes: meaning certification is not a move available to the respondent, and since the instructions are respondent-oriented, the actual meaning of (s) is an external problem.