Is there a \renewtheorem equivalent of \renewcommand, using amsthm and not ntheorem?

Question

Suppose I have a theorem that is defined a certain way, as follows.

\newtheorem*{mytheorem}{Foo}

And I want to redefine it another way further down in my document, as below.

\newtheorem*{mytheorem}{Bar}

What is the easiest way to go about this?

I would like something like this, but I get undefined control sequence on \renewtheorem.

\documentclass{article}
\usepackage{amsmath}
\usepackage{amsthm}

\begin{document}
\theoremstyle{definition}
\newtheorem*{thmTemp}{Foo}
\begin{thmTemp} First one.  \end{thmTemp}

\renewtheorem*{thmTemp}{Bar}
\begin{thmTemp} Second one.  \end{thmTemp}
\end{document}

When I run pdflatex on this, I get the following:

! Undefined control sequence.
l.10     \renewtheorem
                  *{thmTemp}{Bar}

I am avoiding ntheorem because it does not preserve the theorem styles defined by amstheorem, even when the amsthm option is passed to it, and I would prefer not to redefine those styles.

Answer 1

Rather than redefining the environment each time, I would define a wrapper:

\documentclass{article}
\usepackage{amsthm}
\theoremstyle{definition}
\newtheorem*{inner}{\innerheader}
\newcommand{\innerheader}{}
\newenvironment{defi}[1]
 {\renewcommand\innerheader{#1}\begin{inner}}
 {\end{inner}}

\begin{document}
\begin{defi}{Foo}
First one.
\end{defi}

\begin{defi}{Bar}
Second one.
\end{defi}
\end{document}