It is by avoiding the rapid decay into the inert state of "equilibrium", that an organism appears so enigmatic; so much so, that from the earliest times of human thought some special non-physical or supernatural force (vis viva, entelechy) was claimed to be operative in the organism, and in some quarters is still claimed.
How does the living organism avoid decay? The obvious answer is: by eating, drinking, breathing and (in the case of plants) assimilating. The technical term is metabolism. The Greek word means change or exchange.
Exchange of what?
Originally the underlying idea is, no doubt, exchange of material. That the exchange of material should be the essential thing is absurd. Any atom of nitrogen, oxygen, sulphur, etc., is as good as any other of its kind; what could be gained by exchanging them?
What then is that precious something contained in our food which keeps us from death? That is easily answered. Every process, event, happening - call it what you will; in a word, everything that is going on in Nature means in increase of the entropy of the part of the world where it is going on. Thus a living organism continually increases its entropy - or as you might say, produces positive entropy - and thus tends to approach the dangerous stat of maximum entropy, which is death. It can only keep aloof from it, i.e. alive, by continually drawing from its environment negative entropy - which is something very positive as we shall immediately see. What an organism feeds on is negative entropy. Or, to put it less paradoxically, the essential thing in metabolism is that the organism succeeds in freeing itself from all the entropy it cannot help producing while alive.
