Recall from the past chapter (specifically, the section “Computation as metaphor for the exploration of creativity”) that what has been named the computational theory of scientific creativity or CTSC is a hypothesis about the nature of creativity (in the natural and the artificial sciences). This hypothesis is, furthermore, firmly rooted in the computational metaphor – more precisely, it relies on the formation of a metaphorical model connecting creative and computational processes.

It also bears repeating that this theory goes back to Newell, Shaw, and Simon (1962) and, in effect, is a special case of a broader theory of thinking known concisely as the physical symbol system hypothesis (Newell and Simon 1976). The theory also serves as the basis for some recent explanations, by Kulkarni and Simon (1988), Thagard and Nowak (1990), and Thagard (1988, 1990), of certain historically important discoveries in the natural sciences. Thus, the general nature of CTSC is well known and has been so for some time. The task of the present chapter is to articulate and state CTSC in a sufficiently precise form such that (1) the reader understands and can anticipate, at least in general terms, the direction along which the explanation of Wilkes's creativity will proceed in the chapters to follow (especially, in Chapters 4–6) and (2) it is posed as a genuinely testable (i.e., in principle, falsifiable) hypothesis for which the Wilkes case study constitutes a nontrivial test. The extent to which CTSC is, in fact, corroborated or refuted by this test, and the general lessons learned from the case study, are matters discussed in the final part of this book.

There we have it: an account – an explanation – of how a particular act of inventive design in the domain of one particular science of the artificial might have taken place. The explanation takes the form of a computation at the level of cognitive description known as the knowledge level. Just as the proof of a theorem stated as an organized, stepwise set of arguments is an explanation of why the theorem is (believed or should be believed by an individual or community to be) true, so also our explanation takes the form of a symbolic process – that is, a structured set of symbol-transforming actions. Extending this parallel further, just as a mathematical argument draws on a body of assertions (axioms, lemmas, and theorems) that are assumed or known to be true prior to the onset of the argument or are produced along the way, so also the process described in these pages appeals to a corpus of knowledge the tokens of which are in part postulated to have existed at the time Maurice Wilkes began to think about the problem and in part generated by the process itself.

Let us, at this stage, recall a point already emphasized in Chapters 1 and 4. Historical episodes of a certain type bear the stamp of contingency. Past episodes of cognitive acts such as the invention of a theory or the design of a new type of artifact belong to this category. Thus, any explanation of such an episode will inherit the burden of contingency. We can hardly ever claim that the episode must have happened in one particular way rather than some other.

In May 1949, the EDSAC computer, designed and constructed by Maurice Wilkes and his co-workers at the Cambridge University Mathematical Laboratory successfully performed its first, fully automatic computation (Wilkes, 1956, p. 39; 1985, p. 142; Wilkes and Renwick 1949). The machine was demonstrated soon after, in June 1949, at a conference entitled “High Speed Automatic Calculating Machines” held in Cambridge during which tables of squares and primes were printed out (Worsley 1949). As noted in chapter 1 (see the section “The invention of microprogramming: as a case study”), the EDSAC was the very first stored program computer to become fully operational.

The EDSAC was a serial machine in that (1) reading from or writing into main memory was done in a “bit-serial” manner – that is, each bit of a memory word was read or written into one at a time, and (2) the arithmetic unit performed its various operations in a bit-by-bit manner.

Soon after the EDSAC's completion, Wilkes became preoccupied with the issues of regularity and complexity in computer design. This preoccupation is documented not only in his retrospective writings (Wilkes 1985, pp. 184–5, 1986), but also in the early sections of Wilkes (1951), as a preamble to his description of the microprogramming principle. Thus, there is considerable evidence that the development of microprogramming was the outcome of the following problem:

Among the many features of the mind that humans have chosen to speculate on, few evoke a greater sense of enigma than creativity. Believing that as a cognitive act it stands well beyond the humdrum, we pay special homage to those whose occupations are thought to be intrinsically creative: artists, scientists, writers, musicians, and inventors. Recognizing further that even among them there are a few whose works are so very special and so far transcend the achievements of the rest, we accord them extra reverence; we often bestow on them the appellation “genius”; we wonder, sometimes in awe and not without a tinge of envy, about their mental makeup; and we ponder the nature of the process their minds have enacted in arriving at a particular poem, symphony, theory, or artifact.

We see evidence of this compelling interest in creativity in many distinct forms. The very best type of biography, for instance, embodies an engagement on the part of the biographer with his or her subject's life and work. The biographer's task is to comprehend how childhood, social background, worldview, intellectual influences, personal relationships, and so on may have affected, perhaps even serve as an explanation of, the subject's particular acts of creation. In Richard Ellman's (1982) biography of James Joyce, there is a chapter titled “The Backgrounds [sic] to ‘The Dead’” in which the main elements of this short story – its characters, the setting, even the basic plot – are explained or elucidated by Ellman in terms of Joyce's own background and experience.

This brings us to the end of this particular inquiry. We began with a central concern: the nature of creativity as it is manifested in the development or design of artifacts. Not all acts of design count as creative acts. Like ideas and theories about nature or works of literature and art, the creation of artifacts is deemed creative when the outcome is original in some sense. Drawing on a distinction made by Johnson-Laird (1988a), Boden (1991), and others, we saw that it is possible to establish criteria of originality either from the perspective of the individual agent or from that of the society or community to which the agent belongs. When the outcome of an act of design is an artifactual form that satisfies one or more of the criteria of originality, the design act is called inventive or creative design. More simply, we call it invention. Inventing artifactual forms corresponds to discovering laws or inventing theories about natural phenomena. Thus, it seemed reasonable to suppose that studies of creativity in the natural sciences might provide insight into the nature of creativity in the sciences of the artificial.

We saw that philosophy of science, having been primarily preoccupied with the logic of justification, had little to contribute to our inquiry. Fortunately, there has emerged in relatively recent times a new kind of inquiry into scientific activity that draws on the ideas of cognitive psychology, history of science, and artificial intelligence; it was to these sources we turned.

The main ingredients have now been assembled. We have, first, a computational theory of scientific creativity, CTSC. Its central thesis is that a cognitive act resulting in a scientific product – a solution to a scientific problem – deemed original by the originator or by the relevant scientific community can be specified as, or be explained in the form of, a knowledge-level process.

Second, we have a detailed account of the circumstances attending a particular episode from the arena of computer science: the invention of microprogramming. Since computer science is a science of the artificial, one can regard this invention as signifying the creation of a technological idea, the invention of a new artifactual form that satisfies certain functions or, more prosaically, as an instance of highly original design. In the artificial sciences, these views are virtually indistinguishable.

This historical account is as detailed as the documented evidence will allow. And viewed as a historical explanation, it would appear to be satisfactory. That is, to the question What were the circumstances attending Wilkes's invention of microprogramming? the narrative presented in Chapter 3 would constitute an explanation of the sort historians of science ordinarily produce. It identifies the state of affairs that existed regarding computers and computing circa 1950. It then presents the particular problem that exercised Wilkes (i.e., that of regularity and order in the design of the control unit) and describes, in terms of the known state of affairs (specifically with regard to the EDSAC), how or why the problem arose. The narrative then points out that Wilkes was led to the idea of the diode matrix in the EDSAC order interpreter.

The subject matter of this book is creativity in the realm of invention and design. More specifically, it addresses the issues of how significantly original technological ideas or concepts may be produced by individuals. Questions such as this about the nature of the creative process are, of course, far from new. As Brewster Ghiselin pointed out in his introduction to The Creative Process, an anthology of writings on the topic, interest in creativity can certainly be traced back to the Greeks. It has continued to be thought about and written on ever since.

The premise of this book, however, is a relatively modern idea. It is the belief that it is possible to construct plausible, detailed, testable explanatory accounts of the cognitive processes underlying specific past acts of creation – acts such as the discovery of physical laws, the elucidation of biochemical pathways, or the invention of artifactual forms. The basic intellectual tool to be used in such explanations originates in the modern disciplines of cognitive science and artificial intelligence: It is the idea that computation-like processes of a certain, rather abstract kind can serve as a powerful metaphor with which to probe creativity and that, consequently, it is possible to obtain insight into the nature of specific acts of creation in a way and at a level of detail that has hitherto proved infeasible.

The means by which technological creativity is examined in this book is, in fact, a confluence of three distinct strands. One is the case study approach in which a specific episode from the history of computer technology, widely recognized as a highly original landmark, is singled out for study.

Problem recognition and formulation

The reader will recall from the section “The concept of creativity” in Chapter 1, that the criteria whereby a cognitive process P is deemed creative pertains to the nature of the product Π of that process. It is quite easy to be seduced into assuming, when we talk about Π, that we are really referring to a solution to some problem. This need not be so. Π may, in fact, itself be a problem and P the process of identifying it.

That the recognition of a problem and its formulation in a tractable or solvable form is one of the characteristic features of the creative mind – at least in the realm of scientific discovery and invention – is widely acknowledged (Sternberg 1988b; Root-Bernstein 1989). In the case of the invention of microprogramming, we have seen, according to the account in Chapter 3, that Wilkes was not presented with an “open” problem – that is, a problem already identified and acknowledged within the relevant community. He saw a problem others had not seen. The problem, it will be recalled, was conceptual in nature, having to do with such attributes as regularity and complexity. And as noted in Chapter 3 (section “On the conceptual nature of Wilkes's problem”), the recognition of such a problem by an individual is frequently inspired by a personal philosophical stance or set of values. This seems to have been the case with Wilkes, for, as he has remarked, it was essentially a “private” problem for him. Thus, at least in the case of microprogramming, problem recognition and formulation may be said to constitute an integral part of the overall concept formation activity.

In this chapter, I consider the potential and actual reuse opportunities within UNIX. First, several methods are suggested that could increase the likelihood that the next submission matches an item in a small set of predictions offered to the user for review and reuse. All methods are applied to the UNIX traces, and the predictive “quality” of each method is measured and contrasted against the others. In the second part of the chapter, I investigate how well the reuse facilities supplied by the UNIX shell are used in practice.

Conditioning the distribution

In the last chapter, particular attention was paid to the recurrence of command lines during csh use, and to the probability distribution of the next line given a sequential history list of previous ones. We saw that the most striking feature of the collected statistics is the tremendous potential for a historical reuse facility: the recurrence rate is high and the last few submissions are the likeliest to be repeated.

One may predict what the user will do next by looking at those recent submissions. But there is still room for improvement, because a significant portion of recurrences are not recent submissions. Can better predictions of the user's next step be offered? This section proposes and evaluates alternative models of arranging a user's command line history that will condition the distribution in different ways.

The recurrence distributions of Section 5.4.2 were derived by considering all input for a user as one long sequential stream, with no barriers placed between sessions.