The so-called theory of intelligent design (ID) has gained a growing reputation in the Anglo-Saxon culture, becoming a subject of public debate. The approaches that constitute the core of this proposal, however, have been poorly characterized and systematized. The three most significant authors of ID are certainly Michael Behe, William Dembski and Stephen Meyer. Beyond the differences that can be distinguished in the work of each of them, the central fact in their arguments is the complexity of living organisms, which according to these authors, escapes any kind of natural explanation. In effect, according to the authors of ID, the irreducible complexity that can be detected in the natural world would allow to infer design in a scientifically valid way, even though many of them prefer to remain silent regarding the identity and attributes of the designer. We think that under this proposal, remains a deep epistemological confusion, since its very structure combines methodologies that are beyond the scope of historical and natural evolutionary theories. We also reject the claim that ID is a legitimate scientific theory, because it does not exhibit the classical characteristics that a scientific kind of knowledge must have.