We've been getting a bunch of libertarians coming over to the playground in the last week, so it seems an opportune moment to pull out of Emile Durkheim's The Rules of Sociological Method passages that capture the difference between the two views.
Libertarianism is a movement spawning from the Enlightenment in which human beings were seen as discrete atomic rational entities. Just as ping pong balls in a box are subject to Newton's laws that will govern their motion, we are individuals endowed with reason and interests and we use this reason to determine how best to serve our self-interest. In this way, we are well-ordered beings. Our welfare is maximized when our self-interest is best met and being rational, I will always be able to determine for my interests in my context what will best serve my interests. Hence, any interference in my autonomy, any limits placed upon my liberty, will necessarily shut off the best path to my fulfillment, my self-actualization, and therefore should be opposed. as long as contracts are being honored and personal safety is ensured, just leave me alone. I am an atom, let me seek my natural energy state.
Contemporary liberalism, on the other hand, begins by denying this atomistic precondition. It begins by asserting the existence of what Durkheim calls "social facts."
"Here, then, is a category of facts with very distinctive characteristics: it consists of ways of acting, thinking, and feeling, external to the individual, and endowed with a power of coercion, by reason of which they control him. These ways of thinking could not be confused with biological phenomena, since they consist of representations and actions; nor with psychological phenomena, which exist only in the individual consciousness and through it."These are objectively real things which (1) exist outside of individual consciousnesses, and (2) exert a coercive force on the individuals within the society in which the fact exists.
"If I do not submit to the conventions of society, if in my dress I do not conform to customs observed in my country and in my class, the ridicule I provoke, the social isolation in which I am kept, produce, although in attenuated form, the same effects as punishment in the strict sense of the word."There are social facts that are usually not noticed because when we in accord with them, we get left alone or rewards we think we deserve because we exert effort in staying within the socially constructed boundaries. We only feel them when we violate them and the result is either internal (guilt, worry, paranoia) or external (arrest, social shunning, getting turned down for dates).
These social facts are not biological or psychological in that we can resist them (although doing so comes with a cost) and we can shape them by altering aspects of our culture and its institutions. While they do not have deterministic effects on any given person or any given decision, they do have empirically demonstrable statistical effects. It makes it more likely that a person in society X will do X or not do Y. He illustrated this with his work on suicide, clearly a personal decision deeply tied to individual circumstance and choice, but the rates of which predictably increase with certain social factors such as religious mix in an area (the more Protestants in a region, the higher the suicide rate in proportion).
Contemporary liberalism starts from the premise that we do not decide our action from the will of a blank slate endowed with reason, rather we are social beings who are affected in ways we don't realize by forces that result from the structure of our society. In addition, these forces are not randomly distributed, but weigh the cultural dice in the favor of some and against others. This means that advancement is in part the result of unfair capricious causes tied to our social structure, unfairness that can be dealt with by changing the culture.
Think of the hackneyed cliche "leveling the playing field." Libertarianism in its focus on atomic individuals argues that the only thing operative is the players. The playing field is irrelevant. Liberals on the other hand, argue that the playing itself is something that needs to be considered because while it does not force players to move in certain directions, the social facts "on the ground" do make certain moves more difficult and therefore both less likely to be tried by those moving in a certain direction and less likely to be successful. If you have two punters who kick equally well and who have been training equally hard, but one gets to kick with the wind while the other kicks against it, the effects will be different and we shouldn't celebrate the one and condemn the other. Liberals argue that there is a cultural wind. Speed skaters do not start next to one another, but are staggered. Libertarians would argue that one is being given an unfair head start, but in fact because of the social facts governing the lengths of turns on the inside and outside lanes, the seemingly unfair stagger is actually maximally fair.
The difference is a disagreement over the existence and effect of social facts.