A Different Kind of Reasoning for a Different Kind of Problem

In The Sciences of the Artificial, Simon proposed that the natural sciences are concerned with “how things are,” while design is concerned with “how things ought to be.”5 Simon argued that every act of human creation is design—this is what he means by “artificial” as opposed to “natural”—and that everybody is a designer: “Everyone designs who devises courses of action aimed at changing existing situations into preferred ones,” Simon wrote.6

When interviewed in 2009, Nigel Cross, author and professor emeritus of design studies at the Open University, referred to “constructive thinking” as the heart of design practice, which he described as “imagining how something might be, not just how it is.”7

At the heart of this concept of design is a distinct kind of reasoning, which theorists refer to as abductive reasoning, and which differs from the kind of reasoning traditionally used in logic and science, known as deductive and inductive reasoning. The simplest illustration of deductive reasoning goes as follows: If a=b and b=c, then it must logically be the case that a=c. Inductive reasoning, by contrast, draws conclusions based on premises believed to be true: If I have observed swans in a given region, and all the swans observed are white, I may form the rule or prediction that all swans in this region are white.8 The truth is not guaranteed in inductive reasoning as it is with deductive reasoning—black swans certainly exist—but the conclusion is inferred based on evidence. Therefore, there is good reason to believe the conclusion.

Abductive reasoning, on the other hand, was first introduced by American pragmatist philosopher Charles Sanders Peirce in 1901 as “guessing.”9 For example: I come outside and my bicycle is wet. I know that when it rains my bicycle gets wet, so I hypothesize that it may have rained. There are other possibilities, however, so I don’t know for certain. In his 1903 Harvard Lectures, Peirce said: “Deduction proves that something must be; Induction shows that something actually is operative; Abduction merely suggests that something may be.”10 This is important for design because design is the creation of new solutions to a problem, and there is no guarantee that it is the right solution in the scientific or logical sense. It’s always going to be one of many possible solutions. Its rightness is determined by whether it solves the problem. “Abduction,” wrote Cross, “is the logic of design.”11

Design, consequently, focuses on synthesis—the creation of new forms—and as such it is a solutions-based rather than a problems-based approach. As the British mathematician and architect Lionel March put it: “Logic has interests in abstract forms. Science investigates extant forms. Design initiates novel forms.”12 Those engaged in a design process are more likely to spend their time experimenting with a variety of solutions to see if they work, rather than behaving as a scientist might by accumulating as much data as possible, then seeking to discover a formal rule from which a solution might be generated.13