This was posted recently on a skeptic's blog as a response to an attack on vitalism and I thought I'd share it here.
Just as we can distinguish between a computer and the program executed upon it, we can distinguish between the physical and chemical basis of life and life itself. Life acts to preserve the narrow set of conditions that make it possible. It's this activity to conserve and propagate itself which is the vital force. And just as problems with a computer usually aren't hardware malfunctions, illness is most often not a problem with the chemical and physical basis of life, but a disorder of the vital force.