Though honestly, it's common sense. The simple fact of the matter is that free market capitalism (specifically the maddeningly egotistical brand espoused by the followers of Ayn Rand) does not encourage charity, at least on the scale required to affect meaningful change. After all, if I give up money for no gain to myself and my business competitor doesn't, that could be the difference between her business succeeding any mine going under. This encourages me not to be charitable even if I would like to (for reasons of being nice to my fellow man or whatever) or at most only slightly charitable. It's a classic prisoner's dilemma; the best overall outcome is if we both do what's individually less beneficial for both of us.
Why are you only thinking about businesses? What about individuals?
This is honestly my biggest problem with government in general, and with socialism in particular. Socialists love to spout out cliches about how government is "representative." How "we are the government." How "majority rules." To a certain extent, this is correct in every form of government, from direct democracy to a constitutional republic to an outright dictatorship. Even in a dictatorship, the dictator most likely enjoyed the support of the majority at one point or another and certainly enjoys enough support to prevent a coup or revolution or what have you.
So the socialist says, "Look, we've all gotten together and voted that we should have welfare." or "The majority of Americans want unemployment benefits" or whatever. The only thing is, if that were true, government programs would not be necessary. If you're so confident that most Americans want people to be given money even if they don't work, you should be fine with eliminating unemployment benefits, right? All of the majority who believes in those benefits would continue to provide them. If you're convinced that it "wouldn't be enough" (remember, we're constantly told that it already isn't enough), then perhaps the majority doesn't agree after all.
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SmartMuffin - Because anything less would be uncivilized - http://img.imgcake.com/smartmuffin/barkleyjpgde.jpg
http://dudewheresmyfreedom.com/