Engineering Method

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Since the early modern period natural science has been defined in terms of method. The two major approaches to scientific method are those of rationalist deduction and empirical experimentation, analyses of which are often traced back to René Descartes (1596–1650) and Francis Bacon (1561–1626), respectively. Both methods have been argued to have ethical components or to be applicable to ethics. Engineering has been much less described in terms of some distinctive method. In fact, it was only in the mid-twentieth century that discussions of engineering method came to the fore. Interpretations of engineering method are, however, more varied than with science, with less effort to draw connections to ethics, although on both counts the negligence is unwarranted. What follows is a modestly polemical assessment of engineering method that seeks to redress previous oversights by defining engineering method, comparing it with alternative definitions, and establishing the nexus between engineering method and engineering ethics.

The engineering method is "the use of heuristics to cause the best change in a poorly understood situation within the available resources" (Koen 2003, p. 28). Two words in this definition, heuristic and best, are used in an engineering sense. A heuristic is anything that provides a plausible aid or direction in the solution of a problem but is in the final analysis unjustified, incapable of justification, and fallible. Engineering heuristics include mathematical equations, graphs, and correlations as well as the appropriate attitudes for solving problems or minimizing risk in an engineering design. Such attitudes obviously have ethical dimensions. Suggestions to "allocate resources to the weak link," "complete a design by successive approximations," and "make small changes in the state-of-the-art," are also engineering heuristics. Engineers frequently use the synonyms rule of craft, engineering judgment, or rule of thumb to express these experience-based aids that, although helpful, are nonetheless fallible. In France, engineers use the near synonym le pif (the nose); in Germany, faustregel (the fist); in Japan, menoko kanjo (measuring with the eye), and in Russia, na paltsakh (by the fingers).

The engineer'sword best, usually called the optimum, refers to the most desirable tradeoff of the design variables in a multi-variant space in which each criterion has been given its relative importance. This procedure differs from the ideal or best of Plato that is almost universally used in the Western tradition outside of engineering.

This definition of engineering method is consistent with the etymology of the word engineer, its formal definition in the dictionary, and common usage. According to one of England's most noted nineteenth-century engineers, Sir William Fairbairn, the term engineer comes from an old French word s'ingenieur meaning "anyone who sets his mental powers in action to discover or devise some means of succeeding in a difficult task." Contemporary dictionaries concur by authorizing the verb to engineer as "to contrive or plan usually with more or less subtle skill or craft" and by giving examples such as "to engineer a daring jailbreak." The word engineer is used daily in a similar fashion on radio, television, and in the newspaper.

The engineering term state-of-the-art (and its acronym, sota) refers to the collection of heuristics that were appropriate for a specific engineering project at a designated time. Thus, a state-of-the-art CD player will be one that is consistent with the set of heuristics that represented "best engineering practice" at the time it was made.

Derivative of the research in general problem solving (Polya 1945), the most frequent alternate definition of engineering used by engineers involves trying to establish a morphology or structure through which the design process is believed to pass (Dixon and Poli 1995, Pahl and Beitz 1995, Shigley and Mitchell 1983). This morphology is often presented in a flow diagram as in Figure 1. In addition to their multiplicity, engineering morphologies must fail as definitions of engineering because no one argues that the engineer can simply pass through the proposed steps; rather, engineers always back-track, iterate, and expand each step guided by heuristics.

Applied science is the most popular non-engineering definition of the engineering method. For the engineer, however, scientific knowledge has not always been available, and is not always available now, and even if available, it is not always appropriate for use. Some historians credit the Ionian natural philosophers of the sixth century b.c.e. as the founders of science, but undeniably homes, bridges, and pyramids existed before then. Precise scientific knowledge is still unavailable for many of the decisions made by the modern engineer. Although it cannot be said that engineering is applied science, engineers do use science extensively as a heuristic when appropriate.

The related claim that engineering is a branch of science called design science (Hubka and Eder 1996), similar to the social sciences, does not really advance a definition of engineering method. Although the much stronger view that engineering is a branch of science on a par with physics or chemistry is sometimes encountered (Suh 2001), this view implies that there are facts and axioms of design immutable and normed against an eternal truth, just as the facts of physics are said to be undeniably true. By contrast, most practicing engineers agree with the words of the noted engineer Theodore Von Kármán (1881–1963): "scientists explore what is and engineers create what has never been" (Krick 1969, p. 36).

Some, identifying the engineering method with trial and error (Petroski 1994), imply that engineers try random problem solutions and discard those that do not work. Contrary to this view, thousands of design decisions are made worldwide by engineers every day resulting in very few failures because the engineer usually modifies a previously assured sota in creating a new design.

While these alternate definitions are useful in expanding an understanding of engineering, they fail to be convincing as a comprehensive description of engineering method for the reasons specified, and because each can be subsumed into the definition given initially as simply additional engineering heuristics.

Because the engineering method applies to situations that contain uncertainty, some risk of failure is always present. The success or failure of an engineering design is, therefore, not a sufficient basis for judging whether an engineer has acted ethically. The Rule of Judgment in engineering is to evaluate an engineer against the sota that defines best engineering practice at the time the design was made (Koen 2003). This sota must contain all of the appropriate ethical, as well as technical, considerations.

When engineering is recognized as a pluralistic utilization of heuristics to bring about the best change in a limited resource situation that remains to be fully understood, then not only are ethical principles available as useful heuristics but the engineering method can itself become a reasonable description of ethical problem solving in general.


SEE ALSO Choice Behavior;Decision Theory;Engineering Design Ethics;Engineering Ethics;Rational Choice Theory.


Dixon, John, and Corrado Poli. (1995). Engineering Design and Design for Manufacturing: A Structured Approach. Conway, MA: Field Stone. Textbook for upper division engineering students.

Hubka, Vladimir, and W. Ernst Eder. (1996). Design Science: Introduction to the Needs, Scope and Organization of Engineering Design Knowledge. Berlin: Springer-Verlag. Extensive survey of the literature in engineering design.

Koen, Billy Vaughn. (2003). Discussion of The Method: Conducting the Engineer's Approach to Problem Solving. New York: Oxford University Press. This book is the basis of the analysis given here.

Krick, Edward V. (1969). An Introduction to Engineering and Engineering Design. New York: Wiley. One of the original descriptions of engineering design for beginning engineering students.

Petroski, Henry. (1994). Design Paradigms: Case Histories of Error and Judgment in Engineering. Cambridge, UK: Press Syndicate of The University of Cambridge. One of several popularizations of engineering method by this author.

Pahl, Gerhard, and Wolfgang Beitz. (1995). Engineering Design: A Systematic Approach. Berlin: Springer-Verlag. Definitive German morpholophy of engineering design.

Polya, George. (1945). How to Solve It: A New Aspect of Mathematical Method. Princeton, NJ: Princeton University Press. Classic book on general problem solving.

Shigley, Joseph, and Larry Mitchell. (1983). Mechanical Engineering Design, 4th edition. New York: McGraw-Hill. Classic textbook on engineering design for mechanical engineers.

Suh, Nam. (2001). Axiomatic Design: Advances and Applications. New York: Oxford University Press. Defines engineering in terms of axioms as is often done for science.

Taguchi, Genichi; Subir Chowdhury; and Shin Taguchi. (1999). Robust Engineering. New York: McGraw-Hill. The Taguchi method of engineering design is widely used in industry.