 If the treatment of Knot were genuinely the mirror image of that of Tonk, we would be able to say that just as the Knot rules are Cut-inductive but not Id-inductive, so the Tonk rules are Id-inductive but not Cut-inductive. (The twofold demand of Cut- and Id-inductivity is a promising candidate for the notion of harmony as it applies to the relation between right and left insertion rules in a sequent  calculus.[33])  And while the failure of Cut-inductivity was indeed noted, nothing was said on the subject of Id-inductivity for these rules. Spoiling the intended duality, the situation is that the Tonk rules fail on this score too—though this can be remedied by a simple variation. First, we should note that Prior’s point could equally well have been made by combining the ∨ introduction rule from the second (rather than the to first) disjunct with the ∧ elimination rule to the first (rather than to the second) conjunct. Call the connective with these rules Tonk*