Communicated by David Spivak. I invited Edmund Harriss to visit Topos Institute last October, because his work on mathematical art so beautifully exemplified the sort of “working language” I’ve been exploring. Mathematical forms (such as a “perfect circle”) can be conceptually overlaid onto a real-world condition (such as an actual piece of paper) and constrain our behavior enough that the form is efficiently materialized (such as by a computer program hooked up to a mill). I found ...