I thought I should seize the opportunity, because among my interests there is one thread which has preoccupied me for 20 years. Describing this kind of experience can surely yield insight, provided one remembers that it is a personal thread; science is woven from may such threads and is all the stronger when each thread is hard to trace in the finished fabric.
Elements of Interaction by Robin Milner in Communications of the ACM, 1993 January