How can we detect design in nature? One idea, proposed by Michael Behe, is irreducible complexity. Behe explains that a machine is irreducibly complex if it has several different parts which all are necessary. Remove any one of those needed parts, and the machine doesn’t function. An internal combustion engine is irreducibly complexity, for instance. Take away the valve, or the piston, or the spark plug, or the wire, and it does not function. Such machines are not likely to be created by blind natural laws--they require forward-looking thought. Assembly is required, and there is no payback until the final...