I am trying to use the same numbering for theorems, propositions, definitions, etc. This is normally easily be solved by using amsmath and defining these environments and using the same counter:
\newtheorem{theorem}{Theorem}[section]
\newtheorem{proposition}[theorem]{Proposition}
Problem: I am using a journal document class which has theorems, propositions, definitions, etc. already defined in the document class. Thus I need to change the counter after the environments were already defined, something similar to the way one can simply change the numbering format with:
\renewcommand{\theprop}{\arabic{section}.\arabic{prop}}
In my case, the document class is:
\documentclass[twocolumn]{svjour3}
Just found the very simple solution inspired from How to identify the counter of Equation, Theorem, and Section. The solution is to match the counters:
\makeatletter
\let\c@proposition\c@theorem
\let\c@corollary\c@theorem
\let\c@lemma\c@theorem
\let\c@definition\c@theorem
\let\c@example\c@theorem
\makeatother

amsmathdoes not have anything to do with theorem counters; it'samsthm. i'm writing this as a comment instead of editing the question because it's a common misconception, and this might get the point across more clearly. – barbara beeton Dec 31 '12 at 15:32