Three days ago I finally got hold of a copy of Francisco Varela’s paper “A Calculus for Self-Reference”, Int. J. General Systems, 1975, Vol 2. pp. 5-24, including its introduction by Heinz von Foerster and Richard Howe. I have been looking for this for a long time, so I was very happy to find it, only to find out that I should have looked in the right place on-line: without the (short) introduction you can find it right here, on Louis Kauffman’s site. (see previous posts here and here for a bit of context)

In Varela’s paper, he extends the calculus of distinctions by George Spencer-Brown by a third state. It is incredibly interesting to read, but I’ll have to read a lot around this paper to really grasp what it means and what kinds of reasoning it enables. And just as is the case with Spencer-Brown: since this side of things seems very much out of fashion, sources are hard to find (or perhaps I am again not looking in the right places to begin with). I guess the next station will be Varela’s 1979 book “Principles of Biological Autonomy”; I’d like to find a copy I can afford…