Exponential Modalities
The Linear Logic connectives ! (“of-course”) and ? (“why-not”) that re-introduce the structural rules of weakening and contraction in a controlled way: a formula !A is a reusable hypothesis. The exponentials are how classical and intuitionistic logic embed into linear logic — they restore non-linear reasoning locally rather than globally. In the Curry–Howard counterpart for concurrency, !A corresponds to a replicated / shared service: a session offering arbitrarily many copies of A.