During Rand Paul's filibuster, Ted Cruz asked a "question" of Paul (to give the guy a break), Cruz cited Federalist Paper No. 10 as an admonition against the rise of special interest groups. In that classic tract in the field of political science, Madison wrote on the importance of protecting the rights of the minority against the inevitable mob mentality of the majority that would manifest in the government, unless proper safeguards were put in place.
Madison defined a faction as "a number of citizens, whether amounting to a majority or a minority of the whole, who are united and actuated by some common impulse of passion, or of interest, adversed to the rights of other citizens, or to the permanent and aggregate interests of the community."
Madison noted that well-constructed union would be able to "break and control the violence of faction, and that this important because democracies have a "propensity to this dangerous vice."
This is the centerpiece of libertarian philosophy, which states that government exists to protect private property because as, Madison wrote,
"Those who hold and those who are without property have ever formed distinct interests in society. Those who are creditors, and those who are debtors, fall under a like discrimination. A landed interest, a manufacturing interest, a mercantile interest, a moneyed interest, with many lesser interests, grow up of necessity in civilized nations, and divide them into different classes, actuated by different sentiments and views. The regulation of these various and interfering interests forms the principal task of modern legislation, and involves the spirit of party and faction in the necessary and ordinary operations of the government."
Like Karl Marx later on, Madison recognized that society inevitably divides into different classes. Quite obviously, however, Madison and Marx came to very different conclusions on how to respond to this phenomenon.