# What environment to use in writing formal deductions?

Learning about mathematical logic, I have to write formal deductions*.

How can I write them using TeX?

Any feedback is welcome.

(*)Roughly they are numbered lists over two columns, the first one gives a formula and the second one gives its justification (if it is an axiom, a hypothesis or if it is inferred by previous entries), both can go over many rows.
Anyway here is an example (from: Mendelson, Intro. to Math. Logic.)

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Perhaps a tabular environment using a a p{} column type, and a custom counter for the first column? – Peter Grill Jul 27 '12 at 7:33
the notation you're using is very like that used in the article "ProofCheck: Writing and checking complete proofs in LaTeX" by Bob Neveln and Bob Alps. this was presented at tug 2009, and a video is available. you might get some ideas from this. the authors presented an update at tug 2012, but unfortunately, this year's meeting wasn't recorded; the tugboat article will be published in the proceedings issue (but hasn't yet been received). – barbara beeton Jul 27 '12 at 12:21
Have a look at http://www.logicmatters.net/latex-for-logicians/nd . There is a list of solutions for writing logical proofs in LaTeX – Guido Jul 30 '12 at 18:35
As @Guido's link seems broken (missing column?), I repost it here logicmatters.net/latex-for-logicians – Niriel Apr 6 '15 at 14:13

Here is one way to do it using a custom counter for the first column, and the p{} column types for the other two columns:

## Code:

\documentclass{article}
\usepackage{amssymb}

\newcounter{MyRowNumber}
\newcommand*{\NewRow}{\stepcounter{MyRowNumber}\arabic{MyRowNumber}}%

\begin{document}
\begin{tabular}{l p{0.25\linewidth} p{0.25\linewidth}}
\NewRow & $x^2 + y^2 \ge 0\ \forall x, y \in \mathbb{R}$ & Hyp\\
\NewRow & $more\ math$                                   & 10,11 conjunction introduction\\
\end{tabular}
\end{document}
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Thank you, Peter Grill. – Giuseppe Jul 27 '12 at 8:50