## Friday, 11 February 2011

### Writing Mathematics: Formalism obscures intuition?

I have read quite a large percentage of the books that are currently widely available on the topic of writing mathematics, and several that aren't. I've also been involved in teaching the Mathematical Writing course run at the QMUL. There is one serious issue that I've encountered: the main problem seems to be that most people start with the assumption that you already know everything that you're going to write, and the basic structure of your proof, but don't know the best order to put the words on the paper. In my experience, this is far from true.

I'm currently writing up my thesis, and have several new ideas which I've never written down in complete formal detail before. This process is difficult. The ideas in are generally simple enough that I think I could explain them to reasonably bright 15 year old in about 10 minutes given a piece of paper, but sufficiently abstract that to write them down formally has involved pages of writing that even I barely understand. These are proofs that I can (and have) run through in the pub with non-experts on the back of a napkin, and they translate into 10 pages of symbols that even I can barely follow. (I'm working on a post containing an example, but it will require drawing some pictures, so I'll probably get round to it some time over the weekend).

It is all very well saying that one should write an informal verbal summary of what you are going to do before you do it, but when the formalism is so far removed from the key idea, this becomes difficult. Also, when you are writing a maths paper, you have to make damn sure that the "summary" is still technically accurate. There can be no hand-wavey 'look, it just works' and (importantly) no interaction with the audience - you dont' know if they 'get it', so you have to put down everything it might take for them to get it. In my experience, the heavy formalism has often meant that the proofs I write down end up so complicated that I'm not even sure I would 'get' them if I had to pick up the ideas directly from reading the papers. The formalism masks the intuition, and the intuition isn't quite formal enough to be appropriate for the paper.

This is an interesting topic. It's one that several people have no doubt spent a lot of time thinking about, but it's not one that seems to be discussed. Even in a mathematical writing course, the tendency is to focus on technicalities. To be fair, this is usually adequate for undergraduates, and you do need to get the technical stuff right even when writing down simple ideas, but this is something that needs addressing: exposition of mathematics is a difficult skill, and probably one that there's not enough focus on in training academics.

Maybe not everyone has this problem - maybe not everyone has elementary ideas which don't translate nicely into formalisms - maybe their ideas are inherently more technical, or maybe they're just better at finding formalisms than I am - but I do find it interesting that it's happened to me almost every time I've tried to write out a formal version of a proof that I've created myself.

PS - the vast majority of this post was written over a year ago - the posting of it was sparked by having a discussion with Andy in which he mentioned that he is currently having exactly the same problem, and by me finally figuring out how to access the drafts of my old posts...

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