The debate between evolution and intelligent design is usually presented by evolutionary biologists as a clash between science and non-science (creationism and religion) and therefore as a sterile argument which science wins by default. Countering this is intelligent design (ID) and irreducible complexity (IC) which posit that the diversity and complexity of life on earth indicates the hand of a designer, although the nature of that designer is not speculated on. In doing so, proponents of ID and IC bring the argument squarely into the scientific camp and fulfil the requirements of being science, although this is difficult to define. Here, we discuss the claims of ID and IC to provide an alternative to evolution and propose that science can adequately deal with and refute these claims. At the same time, ID and IC fulfil an important role as foils to 'scientism' - the belief that science is the best way of answering all questions. In the final analysis, however, despite their value in the debate, ID and IC are not found to be robust or reliable enough to replace evolution as the best way of explaining the diversity of life on earth.