I have always been a great admirer of Isaiah Berlin, the Russian-Jewish-British political scientist who spent his life cautioning the West about the dangers of coercive systems such as that of the former Soviet Union. In his famous Oxford University inaugural lecture of 1958, "Two Concepts of Liberty," Berlin defined "negative freedom" as freedom from; it is the freedom to do what the heck you please as long as you don't infringe on anyone else. "Positive freedom," on the other hand, is freedom to; it is the freedom of a directive ideal, one that holds up a vision of the good life (whatever that might be) and encourages--or forces--people to conform to that image. Going back to at least the 17th century, negative freedom is the Anglo-Saxon conception of what it means to be free; and as far as Berlin was concerned (as a good British subject--he became Sir Isaiah the year before his inaugural lecture), that was the only freedom around; the other variety, he believed, was inevitably dangerous. The only problem is, without a positive vision of the good life, the good society, what are we? How could we be anything else except a ship without a rudder? This, to me, is the Achilles heel in the Berlinian edifice, for negative freedom finally affirms nothing--as the example of contemporary America clearly demonstrates...There is no doubt, of course, that "vision" can get out of hand; this was Isaiah Berlin's whole point. But what Berlin failed to understand was that lack of vision can also get out of hand, as Harvey Mansfield makes abundantly clear.
I don't think Berlin "failed to understand" that point; I think he simply accepted that we might not be able to hammer out any sort of consensus on what the good life is, how we can achieve it, or what we need to do and when we need to do it. Just like how it was understood early on that a functioning democracy required an informed and engaged citizenry, the possibility (or even likelihood) of failure was always part of the deal. The price of freedom and all that.
And of course, Berlin wasn't merely focused on extreme examples like the former Soviet Union; his point was that when an Enlightenment-derived faith in the ability of reason and science starts to assume that social questions can be investigated and their answers determined with the same sort of accurate practical results that the natural sciences had demonstrated, a refusal or inability to get with the program in any way would eventually lead to some sort of oppression "for your own good", since you were obviously too mentally ill or otherwise deviant to clearly see what you needed to do to fulfill your proper role in the scheme of things. It's the same reason why Sam Harris's latest endeavor has caused such a furious uproar.
Agreement on the nature of the "good life" and the means of living it is never going to be workable beyond small groups anyway, in my opinion; certainly not on the level of a modern nation-state. How could it?