Have thought about this too. Seems that Tolkien created a world in which things run down from a perfect start. Not sure exactly why he chose to do thus, but I can offer my thoughts:
- I would say that some people look to the past as the "golden ages," seeing it glorified in some manner. This view obviously glosses over the rough and bad that also existed in those days. I always find it funny when people tell me that they would have liked to have lived during the pioneer or chivalry/knights ages. These same people can't eat something that an ant crawled on nor go camping without their portable generators.
- His view does follow the Second Law of Thermodynamics (Any system which is free of external influences becomes more disordered with time. This disorder can be expressed in terms of the quantity called entropy.). From Eru to the present, we've gone from one to many many times over.
- If Tolkien were writing a pseudo-history, well, then, he knew where the story had to end, which would be with us and our world as it is in its present state. No orcs, just jerks and sociopaths. No dragons, Balrogs (winged or otherwise), wizards, seeing stones, elves, etc. Surely some might look at dinosaur bones and think of old Glaurung, use cell phones and think of Fëanor, see people of a certain look and think hobbit or elf or dwarf or beornings, etc, but that would be those of us who know what to look for - traces of Middle Earth amongst us.
He also may have included his Christian viewpoint, but I'm not sure that the two map exactly. If one were to read Genesis (the first book of the Bible), one sees a perfect world created which then starts to fall from perfection. All is good until the first two humans sin, which then starts the world spiraling down and away from perfection. The same text speaks of mankind living hundreds of years (the oldest man being Methuselah who lived for 969 years!). Something changes after the noachian flood, afterwhich the average lifespan of man decreased (until recently, when it has started increasing again).
The historical view would be that the world is winding up, in regards to technology and knowledge, and a biological viewpoint would be that the world is simply changing. We might think that we're
all that, but we haven't been here even a tenth of the time that the dinosaurs 'ruled the earth,' and just when was the last time you saw one of them boarding a tram?
Sometime in the future the Christian world will return to perfection, though the scientifc view is that the earth will be swallowed by the sun, which in turn will burn out, and if current physics has it right, the whole universe will run down into silence.
But not to worry, as that's at least a few years from now, and you should continue to save money for the 25th anniversary edition of the LOTR DVDs by Peter Jackson

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