Throughout the history of political thought men and women have proposed ideal solutions to the problems of community life. Many of these are utopian either in fact, or both in fact and intention.
The consequences of such theorizing have been disastrous, sometimes, and misleading most often. Why?
A utopia is an impossible conception of a human community—but one which if not realizable is said to offer at least the guidelines toward improvement. This is why such views are called ideals or idealistic: they are accepted as beyond the realm of reality. (Our use of the term "ideal" reflects this point in many contexts, especially when we call a naive person idealistic.) The origin of utopianism and the corresponding sense of idealism is Plato's theory of knowledge and his political ideal, the republic.
Plato believed that to know something for certain is to know it as it exists in a world different from ours, one that our world can only approximate, never truly reflect. His political philosophy makes reference to the ideal state which is equally unattainable. Yet, the virtues of such a state, just as the virtue of achieving knowledge of Plato's kind of truths, are accepted by him—if only as guiding principles—never to be achieved, but always to be approximated.
As with Plato's theory of knowledge, so with his political philosophy, there are many interpretations of it. But the most popular view about them is that they are good models to follow. (Some even argue that Plato was aware that his political state could not be implemented on earth.
Yet he did want people to strive to get as close to it as possible.)
Now the most important error with utopianism can be seen right here: the view that ideals, though impossible to achieve, can be good guiding principles. In fact they cannot be. Once a guiding principle removes man's mind, and therefore his plans of action, from reality, the substance of man's plans will be unrealistic. One need only think of the "ideals" that have governed Marxist governments, Nazi states, or even our kind of welfare statism, in order to see the consequences of such thinking. Goals are designed with some admitted but supposedly glorious unreality in mind, only to lead to the most real horrors and vices in the process. Sure, in some kind of world a pure race of glorious beasts might be nice to have around. Sure, at some unspecified time when some new kind of human beings populate the world, it might be nice to have everyone do the right thing automatically. And certainly, in some sort of society, although not a human one, the wealth ought to be evenly distributed—as well as beauty, good manners, happiness, and everything we all must work for these days on our own. But that tells us little of what will produce the best life for us, in this kind of world, with human nature as we know it. So the ideals pursued with "good intention" lead the pursuers to make a bigger mess of things then existed when the pursuit began.
Having failed at getting things improved by such hopeless means, many turn around and embrace a cynical pessimism, or "realism", one that denies any possibility of improvement, even the kind that is open to us. So people move from hopeless idealism to crass pragmatism. And once again the conditions of man are unimproved.
The libertarian political philosophy rejects the notion that ideals must be unattainable, that perfect solutions must lie outside the realm of the possible. For the libertarian realizes that ideals are meaningful and pursuable only if they are based on knowledge of the real, of what is the case, and that such ideals that accord with this analysis can be achieved and should be. The realistic guidelines which emerge from such devotion to facts can, then, be followed up and improvements can be made—though never guaranteed.
Nor does the sensible person believe that we need any utopias to guide our political aspirations. We need to recognize that each person has his own level of perfection that he is morally responsible to achieve—and if he does not, he will suffer the consequences right here; if such failure impinges on another's efforts to succeed to the best of his ability, then this will have to be guarded against—which is why the libertarian sees the function of law as the maximum assurance against the violation of the freedom of the individual.
This is not utopianism because this does not guarantee against failure, it does not insure perfect happiness, it does not promise heaven on earth. Politics, for the libertarian, has the minimal function to secure for each person his liberty to make the most of his life—recognizing that he might not do so. And against that there is no insurance.