Ah, this paper is classic... It is a response to the other (equally classic) paper "Why threads are a bad idea" [0].

In fact, threads and events are dual [1], and one can be made as efficient and the other (given a proper implementation).

[0] http://www.stanford.edu/~ouster/cgi-bin/papers/threads.pdf [1] Lauer and Needham. “On the Duality of Operating System Structures” in 1978;