Last week I quoted the philosopher John Dewey on the difference between life and non-living matter. "The most notable distinction between living and inanimate things is that the former maintain themselves by renewal. A stone when struck resists. If its resistance is greater than the force of the blow struck, it remains outwardly unchanged. Otherwise, it is shattered. While the living thing may easily be crushed by a superior force, it none the less tries to turn the energies which act upon it into means of its own further existence." A friend asked why I considered that profound. I'll reproduce here my response, with some very slight re-working. _____________________________ One obvious example of what Dewey has in mind is the immune system in humans and in just about all other creatures with blood coursing through veins. There is a wide range of infections which cause various nasty diseases in humans, whence most of those struck can and do recove...