Presidential inaugural addresses -- or so the editors of The Wall Street Journal tell us -- "usually include calls for national unity and appeals to our founding principles, which is part of their charm." In his second inaugural address Monday, President Barack Obama checked both those boxes -- but he also recited a list of much-cherished progressive talking points, insisting that the government must act -- and soon! -- to curb global warming, redefine marriage and equalize pay between men and women, among other of his presidential priorities.

The specificity of his statements was unexpected for an inaugural address and much remarked by pundits. It was not his specifics, however, but this generality that most struck me:

"America's possibilities are limitless," Obama proclaimed, "for we possess all the qualities that this world without boundaries demands: youth and drive, diversity and openness, of endless capacity for risk and a gift of reinvention."

At first blush, the statement sounds like sheer American optimism -- an expression of the sort of faith in American ingenuity and resourcefulness that has been at the heart of the American Dream since the Founding.

Upon closer examination, however, it's as clear an articulation of what economist Thomas Sowell calls "the unconstrained vision" of man as I have ever read.

In his book A Conflict of Visions, Sowell divides many of the past two centuries' greatest thinkers into two camps: Those whose political theories incorporate man's constraints (e.g. his ignorance, his selfish impulses, his tendency to sickness and death, etc.) as a central feature and those whose political theories ignore these constraints and assume instead that, even if man is not quite perfect, he is, at least, perfectible.

The first, Sowell says, have a "constrained vision," the second an "unconstrained vision."

In a single statement, the president refers to "limitless possibilities" and "this world without boundaries." Sounds like a pretty unconstrained vision to me.

The language of the unconstrained vision -- as proved by the president's exciting statement -- is very appealing. Who wants to accept that -- no matter how great our "youth and drive, diversity and openness, capacity for risk and gift for reinvention" -- we will never be perfect? Who wants to accept that we will never know everything, never be able to do everything, never be everywhere all at once? More mundanely, who wants to accept that ignorance, hunger, thirst, want will always be present in even the most advanced of civilizations?

The trouble with an "unconstrained vision" of man, however, is that -- until that distant day when man is, in fact, perfect and routinely chooses in all things the wisest option available to him -- there can be no pause in our efforts to perfect society. Trade-offs are not acceptable; an absolute "solution" to any "problem" can and must be found -- and, if the costs of that solution are unbearably high initially, then so be it. The costs will have been worth it when perfection is at last attained.

Historically, public policies that aim for perfection not only have not yielded it, but have cost societies more than they could afford -- in both dollars and in other collateral damage.

Sowell writes, in contrast, of the constrained vision:

[T]he constrained vision sees the evils of the world as deriving from the limited and unhappy choices available, given the inherent moral and intellectual limitations of human beings. For amelioration of these evils and the promotion of progress, they rely on the systemic characteristics of certain social processes such as moral traditions, the marketplace or families. They conceive of these processes as evolved rather than designed -- and rely on these general patterns of social interaction rather than on specific policy designed to directly produce particular results for particular individuals or groups.

Processes -- "moral traditions, the marketplace or families," among others -- might not be as exciting as results, but they're more sustainable. More importantly, they require no concentration of power to facilitate the imposition of solutions. They leave us free to pursue the good ourselves -- and to appreciate it.