Concrete Abstractions

At ®rst glance, the title of this book is an oxymoron. After all, the term abstraction refers to an idea or general description, divorced from physical objects. On the other hand, something is concrete when it is a particular object, perhaps something that you can manipulate with your hands and look at with your eyes. Yet you often deal with concrete abstractions.

Consider, for example, a word processor. When you use a word processor, you probably think that you have really entered a document into the computer and that the computer is a machine which physically manipulates the words in the document. But in actuality, when you ªenterº the document, there
is nothing new inside the computerÐthere are just different patterns of activity of electrical charges bouncing back and forth. Moreover, when the word processor ªmanipulatesº the words in the document, those manipulations are really just more patterns of electrical activity. Even the program that you call a ªword processorº is an abstractionÐit's the way we humans choose to talk about what is, in reality, yet more electrical charges. Still, although these abstractions such as ªword processorsº and ªdocumentsº are merely convenient ways of describing patterns of electrical activity,they are also things that we can buy, sell, copy, and use.