Many developers will have heard of Barbara Liskov, through her appearance in Robert C. Martin's SOLID list of design principles. The abstract of her 1994 paper with Jeanette Wing, A Behavioral Notion of Subtyping, makes the principle sound easy in, well, in principle.

When the author of these words started its career as a software developer, "object orientation" was all the rage. "Serious" programming languages were object oriented. "Professional" programming environments allowed one to view "objects" and "classes" in all of their glory. Inheritance, not composition, was the way of the future. Design patterns names were the answer to actual interview questions.

The Kernighan and Ritchie book opens with the "Hello, World" example. The C++ Programming Language follows an annotated table of contents with "The purpose of a programming language is to help express ideas in code." Cox, on the other hand, opens with the story of Eli Whitney and the industrial revolution.

Somehow we all agree about the importance of history in our society. We teach it to our younger ones, we quote it in our speeches, we talk about it during our dinners. Maybe it is because we had to memorize the names of battles fought ages ago, and we expect to capitalize on that fact so as to appear wise (if not arrogant) to others. We might even agree with history itself, shaking our heads in dismay to some extent, as we see the events unfolding nowadays. A phenomenon which, by all measures, tends to increase with age.