The field of design theory is separated to two warring camps. On the one side are people following Donald Schön’s (1983) “Reflective Practitioner;” an epistemology of practice based on a close examination of what different practicioners actually do. On the other side, sometimes angrily denounced by Schön and his followers, is Herbert Simon’s “Sciences of the Artificial” (1969, 1996). Simon, one of the founders of cognitive science and perhaps most famous for his theory of bounded rationality, presented an instrumental theory of design: design as fundamentally a problem-solving activity, or “search” for better solutions in a “design space” of all possible designs. (Note that “design” here refers to all kinds of purposeful activities for designing something, from organizations to policies to products.)
Schön, and later authors, attacked Simon’s view of design as problem solving as “technical-rationality” and “optimizing,” which was – according to Schön – something that simply didn’t happen in real life. Later authors in the field of design theory have largely followed Schön’s lead, dismissing Simon and claiming he did not have much anything useful to say about how design happens.
That this is based on a misrepresentation of what Simon was actually saying is evident if one reads a later edition (e.g. 1996) of Simon’s groundbreaking book. Simon’s theory is far from its caricature as naive linear search for solutions. It’s not “programming” as some (e.g. Hatchuel and Weil 2009) claim; it’s not about fixed goals, it’s not about well defined objects. In fact, it’s somewhat ironic that accusations of “optimization” and trust in the rationality of design decisions were levelled against Simon, who after all received his Nobel price in 1978 precisely for pointing out that humans cannot be perfectly rational, as tacitly assumed under most neoclassical economic theories.
What Simon says is simply that design can be conceptualized as a problem-solving activity, that problem-solving activity can be conceptualized as a search process through immensely vast design space of possible solutions, and in principle, search can operate through simple algorithms or bundles of such algorithms. This conceptualization makes purposeful design (as done by humans) directly comparable to generalized Darwinian “design” or problem-space search, also accomplished through repetitive use of relatively simple algorithms. For a very good discussion and a compelling argument that the “design space” of biology and technology are unitary, see Dennett (1995): Darwin’s Dangerous Idea. (Extremely good if philosophically rather heavy reading anyway!)
For a very good reconciliation of Schön’s and Simon’s views, see Meng (2009): Donald Schön, Herbert Simon and The Sciences of the Artificial, Design Studies 30:60-68.