\leftmargin length not working in enumerate environment

Question

I need to write down arguments that are made up of numbered claims and where the conclusion is marked by a conclusion symbol. I have no problem modifying the way enumerate labels are displayed to have that result.

Unfortunately, these labels quickly get so wide that they hang over into the left margin. I'd like to indent the enumerate environment on the left so that the labels and the text are further to the right. Looking at a list of lengths in list environments (e.g., in this answer), I figured \leftmargin would be the right length for me to manipulate. Unfortunately, it doesn't have the expected effect of indenting the text associated with an item. I can use \itemindent to indent the label, but that only indents the first line, not the main body.

A couple of constraints on answers.

• I'm aware of the enumerate package and for various reasons do not want to use it.
• I only want some, but not all, enumerate environments to be indented in this way. So a global change, e.g., by including \AtBeginDocument{\addtolength{\leftmargini}{3em}} won't work for me.

Here's an MWE I'm working with, and a screenshot of the result. I'm using lipsum as an easy way to generate multiline text, and I'm calling amssymb to get me the "conclusion" symbol of the three dots.

\documentclass{article}

\usepackage{lipsum}
\usepackage{amssymb}
\begin{document}

\lipsum[1]

\begin{enumerate}
  \renewcommand{\theenumi}{\roman{enumi}}%
  \renewcommand{\labelenumi}{(\theenumi)}%
  \addtolength{\leftmargin}{5em}
  \addtolength{\itemindent}{3em}
\item \lipsum[4]
\item \lipsum[4]%
  \renewcommand{\labelenumi}{$\therefore$(\theenumi)}%
\item \lipsum[4]
\end{enumerate}
\end{document}

Answer 1

You do not need to set \addtolength{\leftmargini}{3em} in the preamble it is a local declaration so can be set at any point before the special list. You can reset the value after the list either by using a tex group or simply subtracting the value after the list finishes.

It needs to be before \begin{enumerate} not after as the value is used within the begin code to set up the list parameters.

Answer 2

With enumitem is simple:

\documentclass{article}
\usepackage{lipsum}

\usepackage{amssymb}
\usepackage{enumitem}
\setlist[enumerate]{label=(\roman*),
                    itemindent=3em,
                    leftmargin=2em, % leftmargin=* if you like to have left margin as in main text
                    }

\begin{document}
\lipsum[11]

\begin{enumerate}
\item   \lipsum[4]
\item   \lipsum[4]%
\stepcounter{enumi}          % <---
\item[$\therefore$\theenumi] % <---
        \lipsum[4]
\end{enumerate}
\end{document}

Answer 3

Is it what you want? I set the label width with enumitem, and asked to calculate the left margin in accordance:

\documentclass{article}
\usepackage{showframe}
\renewcommand{\ShowFrameLinethickness}{0.4pt}
\usepackage{enumitem}
\usepackage{lipsum}
\usepackage{amssymb}

\begin{document}

\lipsum[1]

\begin{enumerate}[labelwidth=2.5em, leftmargin=!]
\item \lipsum[4]
\item \lipsum[4]%
\item[$\therefore$ \stepcounter{enumi}(\theenumi)] \lipsum[4]
\end{enumerate}

\end{document}