Published online by Cambridge University Press: 12 December 2024
For relevant logics, the admissibility of the rule of proof $\gamma $ has played a significant historical role in the development of relevant logics. For first-order logics, however, there have been only a handful of
$\gamma $-admissibility proofs for a select few logics. Here we show that, for each logic L
of a wide range of propositional relevant logics for which excluded middle is valid (with fusion and the Ackermann truth constant), the first-order extensions QL
and LQ
admit
$\gamma $. Specifically, these are particular “conventionally normal” extensions of the logic
$\mathbf {G}^{g,d}$, which is the least propositional relevant logic (with the usual relational semantics) that admits
$\gamma $ by the method of normal models. We also note the circumstances in which our results apply to logics without fusion and the Ackermann truth constant.