I'm using lplfitch.sty to produce Fitch-style natural deduction proofs. I want to use different symbols from the ones that are predefined. Specifically, I want to use \sim instead of \neg for negation, and \supset instead of \rightarrow for the conditional. How can I change these?

1 Answer 1


The command you don't like is defined with a simple \newcommand:


Just modify it definitions to suit your tastes:


You'll next want to redefine \lnot:


(note that \mathord is necessary as \sim is considered a binary relation symbol otherwise).




$\uni{x}{\exi{y}{(P(x)\lif \lnot Q(x,y))}}$


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