of the flagellum must have been generated completely at random, a scenario that biologists do not seriously consider. He justifies this approach by appealing to Michael Behe's concept of "irreducible complexity" (IC), which leads him to assume that the flagellum could not come about by any gradual or step-wise process. The validity of Dembski's particular calculation is thus wholly dependent on Behe's IC concept, and therefore susceptible to its criticisms, of which there are many. To arrive at the ranking upper bound of 1020 patterns, Dembski considers a specification pattern for the flagellum defined by the (natural language) predicate "bidirectional rotary motor-driven propeller", which he regards as being determined by four independently chosen basic concepts. He furthermore assumes that English has the capability to express at most 105 basic concepts (an upper bound on the size of a dictionary). Dembski then claims that we can obtain the rough upper bound of for the set of patterns described by four basic concepts or fewer. From the standpoint of Kolmogorov complexity theory, this calculation is problematic. Quoting Ellsberry and Shallit "Natural language specification without restriction, as Dembski tacitly permits, seems problematic. For one thing, it results in the Berry paradox". These authors add: "We have no objection to natural language specifications per se, provided there is some evident way to translate them to Dembski's formal framework. But what, precisely, is the space of events Ω here?" Criticism The soundness of Dembski's concept of specified complexity and the validity of arguments based on this concept are widely disputed. A frequent criticism (see Elsberry and Shallit) is that Dembski has used the terms "complexity", "information" and "improbability" interchangeably. These numbers measure properties of things of different types: Complexity measures how hard it is to describe an object (such as a bitstring), information is how much the uncertainty about the state of an object is reduced by knowing the state of another object or system, and improbability measures how unlikely an event is given a probability distribution. On page 150 of No Free Lunch Dembski claims he can demonstrate his thesis mathematically: "In this section I will present an in-principle mathematical argument for why natural causes are incapable of generating complex specified information." When Tellgren investigated Dembski's "Law of Conservation of Information” using a more formal approach, he concluded it is mathematically unsubstantiated. Dembski responded in part that he is not "in the business of