As a percentage of income, how much money should the government be able to take from you in taxes?

I can't think of any economic-relate topic now so today I searched on Google for some economic journal topics. There is one interesting topic: as a percentage of income, how much money should the government be able to take from you in taxes? (from: http://712educators.about.com/od/Journal-Writing/a/Economics-Journal-Topics.htm)

Taxes are one of the government revenue sources. As a taxpayer, I really want to answer this question be the answer "0%". But, realistically, if we don't pay taxes then the country can't function. So, the alternative answer would be: "5%". Some people might argue that this is not enough, the portion is too little, or the government still can't function.Yet, the government can invest the money and make it into a larger amount (yayyyy!......though I am not sure if the government can do that).