2. (Therefore) the presence of irreducible complexity is a defeasible guarantee of intelligent design.
3. There is irreducible complexity in the natural world.
4. Therefore there are elements in the natural world that are the product of intelligent design .
Behe's argument for ID is extremely bold and rather controversial. So it is important to decide whether his "scientific" claim, can in fact, be supported by factual evidence. An important aspect in Behe's argument center's around the idea of irreducible complexity being evidence of intelligent design. Therefore, it is necessary to understand what is meant by the term "irreducibly complex" and when one is justified in inferring intelligent design. .
According to Behe Irreducible complexity is evidence of ID. However there are two possible interpretations of what he means by irreducible complexity. The firsty interpretation, the one explored in this paper, is as follows: A system is irreducibly complex if it can be "composed without remainder" . This means that every single element of a machine is necessary and if any element were missing then the machine would cease to function. As stated by Behe " each and every piece of a machine, mechanical or biochemical, must be assembled in plain form before anything useful can emerge." Or an alternative second reading of Irreducible complexity (less likely intention of Behe) is as follows: A system is irreducibly complex if it is composed "with remainder". Basically this means that because there exist single vital parts that contribute to the function of something then one could automatically infer ID. E.g. a heart or lungs or a brain could be considered to be a vital part because if any of them were to be taken out of a human then the person would cease functioning. .
However contrary to Behe, Darwinism asserts that irreducible complex systems can be formed as a result of "numerous, successive, slight modifications" (or step by step) via the process of evolution.