According to the enthusiasts for ID, metabolic systems, such as the clotting cascade, are too complex ("irreducibly complex" in their preferred wording) to have arisen through evolution.2 Problems with this view are readily apparent. First, complexity is problematic to define, and irreducible complexity more so.
At present, it is doubtful whether it is possible to measure, prospectively and precisely, the complexity of biological systems so as to distinguish systems that are irreducibly complex from those that are reducibly complex. The concept of irreducible complexity is simply asserted; it is not based on either evidence or compelling logic. Consequently, proponents of ID must decide, essentially arbitrarily, what is too complex to have evolved. They can claim that all of life is too complex to have evolved. Or, are we to believe that bacteria evolved but that humans (or mammals, or whatever groups of organisms) were designed? Would it make any more ...
