Leland, O'Brien, and Rubinstein knew they did not live in what Leland called "a Black-Scholes world" (Leland 1980, p. 580), a world in which market conditions were as posited by option theory. As portfolio insurance was molded from idea to product, the underlying theory was developed to incorporate some of reality's imperfections.

Donald MacKenzie, An Engine, Not a Camera, loc. 797