 The present example comes from the relevant logic R. The sentential constants T and t whose sequent calculus treatment we saw in Section  3  are treated in axiomatic developments of R by means of the axiom schemas φ → T for the former cases and both t and t → (φ → φ), though these last two can be replaced by φ ↔ (t → φ). Here ↔ itself can be regarded as an abbreviation either of (φ → ψ) ∧ (ψ → φ), or as (φ → ψ) ○ (ψ → φ), where ∧ and ○ are the additive or ‘extensional’ (as the relevance tradition would have it) conjunction and the multiplicative or ‘intensional’ conjunction (also called fusion) respectively. While in linear logic neither p ○ q nor p ∧ q provably implies the other, in R, thanks to the presence of contraction, the latter implies the  former.[46]  A well-known further side effect of contraction is that φ ○ ψ and φ ∧ ψ are also equivalent whenever φ is an implicational formula and ψ is its converse, so the two alternative readings of φ ↔ ψ above are equivalent in R. Now consider the possible existence of a new nullary connective for R in the ‘truth constants’ family, T, subject to the axiom schema: