  Different versions of the inferential characterization approach make different decisions about these matters, and these differences affect which constants get certified as “logical.” For example, if we use single-conclusion sequents with the standard rules for the constants, we get the intuitionistic connectives, while if we use multiple-conclusion sequents, we get the classical connectives (Kneale 1956, 253). If we adopt Došen’s constraints on acceptable rules (Došen 1994, 280), the S4 necessity operator gets counted as a logical constant, while if we adopt Hacking’s constraints, it doesn’t (Hacking 1979, 297). Thus, if we are to have any hope of deciding the hard cases in a principled way, we will have to motivate all of the decisions that distinguish our version of the inferential characterization approach from the others. Here, however, we will avoid getting into these issues of detail and focus instead on the basic idea.