Still the most common criticism of Intelligent Design is perhaps the "god-of-the-gaps" rejoinder, that it is an argument from ignorance. Barry Arrington offers a twofold rebuttal. First, ID is an abductive form of argument, an inference to the best explanation based on three defensible premises. 1) Living things display irreducible complexity and functionally specified complex information. 2) Material forces have never been shown to produce either of these characteristics in a living system. 3) Intelligent agents routinely produce irreducible complexity and functionally specified complex information. Intelligent design, therefore, is, in his view, a justified abductive inference. Secondly, he argues that ID's critique of Darwinism rests not on an absence of evidence but rather the evidence of absence. When there is a justified expectation that evidence should be forthcoming for a claim, the absence of evidence is in fact telling. In the case of Darwinism, Arrington concludes that in spite of a legion of well-funded scientists searching tirelessly for 150 years, the effort to find evidence for undirected material forces producing irreducible complexity and functionally specified complex information has "failed utterly".