....
Well, yeah, the fall of the Roman empire was a huuuuge thing with lots of problems going on at once. I wasn't solely blaming Christianity, merely bringing it up because a. I'm Izzy. I do that with Christianity. b. it really does demonstrate how ignorance (willful, forced, or just plain ignorance) can contribute to the decline of something great. Plausible reasons why the Roman Empire actually fell:
1. Only a handful of people (mainly those ruling it) actually believed the civilization was worth saving. The overwhelming majority had been methodically excluded from political responsibilities. These people were vulnerable to attacks because they weren't able to protect themselves. They couldn't serve in the army because they were either too old or no one would be able to uphold their farms when they were away. Their economic situation was.... hopeless. A lot of the people were serfs, who couldn't do anything to help even if they wanted to.
2. While the empire was still expanding, it grew more and more prosperous because it was fed by the wealth and new markets in the new provinces. However, when expansion ceased, economic progress ceased as well, and the economy quickly became really crappy.
3. I would be off on the numbers, but wasn't the Roman Empire like 1/3 - 2/3 slaves? Slaves could sort of be compared to the illegal immigrants in the US today. Their abundance and willingness to work at low wages put Roman Citizens out of their jobs, so they'd seek work elsewhere, and unemployment rates sky-rocketed.
4. Sorta like the Christianity thing.. but.. taxes started being used for a government-run welfare system, and private enterprises were crushed. People learned to except things for no work, so the old Roman virtues of self-reliance and initiative were lost. The more responsibility the government took over from its citizens, the weaker the citizens became.
5. Very little of the Roman army, at the point of its decline, was actually composed of Romans. Who better to fight for you than someone who doesn't give a crap about you, right?
6. Man.. what were they called.. my history teacher would kill me. The Huns, Visigoths.. uh.. Vandals, Anglo-Saxons... uh... yeah, those dudes + more dudes essentially invaded at the same time. Since their army was already weakened at this point, it didn't take long for them to go kaput.
...But if not for Christianity, people wouldn't have sat around blinding themselves to these problems whilst doing nothing.
/history lesson