CV: Adages & Coinages



Tesler's Law of Conservation of Complexity (ca. 1984). “Every application has an inherent amount of irreducible complexity. The only question is: Who will have to deal with it—the user, the application developer, or the platform developer?” Please visit the Complexity Law page.

Tesler's Theorem (ca. 1970). My formulation of what others have since called the “AI Effect”. As commonly quoted: “Artificial Intelligence is whatever hasn't been done yet”. What I actually said was: “Intelligence is whatever machines haven't done yet”. Many people define humanity partly by our allegedly unique intelligence. Whatever a machine—or an animal—can do must (those people say) be something other than intelligence. The theorem is cited in this SlashDot discussion and in these books:

Gödel, Escher, Bach: An Eternal Golden Braid by Douglas R. Hofstadter, Basic Books (1979, updated 1999), p. 601

Foundations of Computer Technology by Alexander John Anderson, CRC Press (1994), p. 395

Real-Time Systems Engineering and Applications edited by Michael Schiebe and Saskia Pferrer, Springer (1992), p. 398


The word modeless to mean a user interface in which the user is never “stuck” in a mode (ca. 1970). Others, including Alan Kay, began to use the term with the same meaning at around the same time. An early example was the Gypsy text editor (1974) that I developed with Tim Mott at PARC. See also About Face 3: The Essentials of Interaction Design by Alan Cooper, Robert Reimann and David Cronin, Wiley (2007), p. 425.

The term friendly user interface has been attributed to me (ca. 1974 at PARC). The first known usage in a publication was "The Office of the Future", Business Week (30 June 1975), p. 48, in a story about PARC. My earlier usage of the term is cited in a quote by Robin Kinkead in Paper Prototyping: The Fast and Easy Way to Design and Refine User Interfaces by Carolyn Snyder, Morgan Kaufmann (2003), p. 47. However, I have seen evidence that use of the similar and somewhat more commonly used phrase “user-friendly” preceded the 1975 publication.

The word browser (1976) to mean a point-and-click information navigation window. The first known window to bear that name was the multi-paned Smalltalk Browser (1976) that I conceived, named and implemented to navigate through a source code hierarchy.

Adages & Coinages