Irreducible complexity is a term used to describe a characteristic of certain complex systems whereby they need all of their individual component parts in place in order to function. In other words, it is impossible to reduce the complexity of (or to simplify) an irreducibly complex system by removing any of its component parts and still maintain its functionality. The otherwise benign concept of irreducible complexity incites fierce controversy when it is applied to biological systems. This is because it is seen as a challenge to Darwinian evolution, which, needless to say, remains the dominant paradigm in the field of biology. Charles Darwin conceded, `If it could be demonstrated that any complex organ existed, which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down` (Origin of Species, 1859, p. 158). Michael Behe argues, `An irreducibly complex system cannot be produced directly (that is, by continuously improving the initial function, which continues to work by the same mechanism) by slight, successive modifications of a precursor system, because any precursor to an irreducibly complex system that is missing a part is by definition nonfunctional` (Darwin's Black Box, 1996, p. 39).