In a Gentzen system (i.e. sequent calculus) for Intuitionistic Linear Logic (from now, ILL), given the usual rules for ILL ($\wedge L, \wedge R, \circ L, etc.$), I want to prove that the Identity $A \vdash A$ may be proved from the instances of identity using atomic propositions alone.
It follows a proof on the complexity of formulas. For $Conjunction$ we have:
$\quad A\vdash A \qquad B\vdash B $
$———————————— \; [\wedge L] $
$A\wedge B\vdash B\qquad A\wedge B\vdash B $
$ ———————————— \; [\wedge R] $
$ \qquad A\wedge B\vdash A\wedge B$
The rules for $Negation$ are the following two:
$ X \vdash A$
$ ———————————— \; [\neg L] $
$ X; \neg A \vdash $
$\;$
$ X; A \vdash $
$ ———————————— \; [\neg R] $
$ X \vdash \neg A $
So, my proof (and my problem) in this case is:
$\;$
$ A \vdash A$
$ ———————————— \; [\neg L] $
$ A; \neg A \vdash $
$ ———————————— \; [??] $
$\neg A; A \vdash $
$ ———————————— \; [\neg R] $
$ \neg A \vdash \neg A $
$\;$
Where I put the question marks is the line that I find problematic. Am I allowed to assume some sort of structural commutativity or exchange in ILL?
Thanks.