# Suggestions for nested proofs

I would like to write down my lecture notes. The proofs of the theorems in this lecture are usually really big. It usually looks like this:

Theorem 1: Here comes the statement of the Theorem

Proof.

1. Without loss of generality let us assume...
2. Claim 1: Statement.

Proof: Blah blah \endOfInnerProofSymbol

1. Claim 2: Statement.

Proof. Blah blah \endOfInnerProofSymbol

\endOfProofSymbol

So my question is now, how can I make such nested proofs with another QED-symbol than the parent proof (maybe a filled square)?

• Welcome to TeX.SX! I'm quite sure this has already been discussed. Commented Jan 20, 2015 at 0:17

You can simply define a new environment subproof that mimics the behavior of proof but uses a filled square instead of the default one.

\newenvironment{subproof}[1][\proofname]{%
\renewcommand{\qedsymbol}{$\blacksquare$}%
\begin{proof}[#1]%
}{%
\end{proof}%
}


You can even give it the optional argument as in

\begin{subproof}[Subproof]


so to print "Subproof" instead of "Proof".

MWE (note the \item after the outer proof to let enumerate start on a new line)

\documentclass{article}
\usepackage{amsthm,amssymb}

\newtheorem{theorem}{Theorem}

\newenvironment{subproof}[1][\proofname]{%
\renewcommand{\qedsymbol}{$\blacksquare$}%
\begin{proof}[#1]%
}{%
\end{proof}%
}

\begin{document}
\begin{theorem}
Here comes the statement of the Theorem
\end{theorem}
\begin{proof}
\item
\begin{enumerate}
\item Without loss of generality let us assume...
\item Claim 1: Statement.%
\begin{subproof}[Subproof]
Blah blah
\end{subproof}
\item Claim 2: Statement.%
\begin{subproof}
Blah blah
\end{subproof}
\end{enumerate}
\end{proof}
\end{document}


• Wow, this is exactly what I was looking for. Thank you very much for this detailed answer!
– aexl
Commented Jan 21, 2015 at 1:22
• I would use \renewcommand{\qedsymbol}{\ensuremath{\blacksquare}} in case \qedsymbol is used in math mode. This will not happen in the definition of proof environments (that I know of), but just to be sure.
– hife
Commented Jan 9, 2020 at 11:29