Generally, it is said that the two parties system are there to defend two ideas:
One is that we can take care of ourselves and live without the government telling us all we must do all the time and, instead, the government would just be taking care of the most urgent and important matters, like security, road building and perhaps education, while the Americans would do all the rest.
The other idea is that men need to be constantly be regulated and told what to do, otherwise, bad things could happen. So it's needed higher taxes so the government can spend money on what they thing to be the best for the citizens.
Generally speaking, our 2 party systems was never desirable and, in fact, our founding fathers warned us about it. John Adams and George Washington agreed that having a 2 party system would not be a good thing for the nation.