…is very interesting. I can’t find anything from the Representational Granularity project online but I did find this:
Domain Extension and the Philosophy of Mathematics
The Journal of Philosophy
Vol. 86, No. 10, Eighty-Sixth Annual Meeting American Philosophical Association, Eastern Division (Oct., 1989), pp. 553-562
I wondered whether this guy was any good and had a look for his name in the extended bibliography that they helpfully put in the back of Tymoczko’s New Directions in the Philosophy of Mathematics, and there this exact paper was.
I’ve found reference to these two:
Manders, Kenneth. 1996. Diagram Contents and Representational Granularity. In: Seligmann, Jerry; Westerstahl, Dag (eds.). 1996. Logic, Language and Computation. Stanford: Stanford University Press.
Manders, Kenneth. 2008. Diagram-based Geometric Practice. In: Mancosu,Paolo (ed.). 2008. The Philosophy of Mathematical Practice. Oxford: Oxford University Press.
But haven’t found them.