I've just got a copy of Engels paper now so I will try to read it over the next few days. By mathematics I don't necessarily mean equations. I see logic and descrete mathematics (including graph theory) as important modelling tools that can be used to specify and simulate complex systems. What the mathematisation gives is a formalisation that tries to ensure concepts can be clearly expressed, understood and reasoned about. Finding the right conceptual framework (and hence formalisation) for a given problem can be hard and sometimes becomes the key to the correct understanding of a system. I have problems with descriptive text where the meaning can be reinterpreted over the years and where vagueness in the arguments makes it hard to confirm or deny statements let alone check for the internal consistancy of an argument.