The limits of materialism. Scott Carson has the latest:

The latest issue of Nature (08/16/2007) has an interesting cover headline: “Form Follows Function” introduces an article by Johannes Hermann called “Structure-based activity prediction for an enzyme of unknown function” that argues, in effect, that the function of a certain enzyme can be predicted on the basis of its underlying structure. This is an interesting finding to Aristotelians, who think that there are such things as essences in nature that do, in fact, determine the functions of things…

To make a long story short, it seems that we have some grounds here for thinking that strictly reductive, materialist accounts of systems are insufficiently explanatory of mechanism: form is also a necessary component of a full explanation.