Scott Klusendorf, a master pro-life apologist, includes a pithy quote in his May 23rd blog post on the personhood of human embryos:
The critical difference between a collection of cells and a living organism is the ability of an organism to act in a coordinated manner for the continued health and maintenance of the body as a whole. It is precisely this ability that breaks down at the moment of death, however death might occur. Dead bodies may have plenty of live cells, but their cells no longer function together in a coordinated manner.
I have got to commit this one to memory, verbatim. It certainly will help me respond to arguments from small size (like Michael Kinsley’s).