Murray Gell-Mann, Seth Lloyd

Paper #: 03-12-068

It would take a great many different concepts - or quantities - to capture all of our notions of what is meant by complexity (or its opposite, simplicity.) However, the notion that corresponds most closely to what we mean by complexity in ordinary conversation and in most scientific discourse is “effective complexity.” In nontechnical language, we can define the effective complexity (EC) of an entity as the length of a highly compressed description of its regularities [6,7,11]. For a more technical definition, we need a formal approach both to the notion of minimum description length and to the distinction between regularities and those features that are treated as random or incidental.