At this month's Conservative Political Action Conference, two up-and-coming Republicans, Senators Marco Rubio of Florida and Rand Paul of Kentucky, provided succinct compare-and-contrast sound bites about how to fix the party.

Here's Rubio: "We don't need a new idea. There is an idea. The idea is called America. And it still works."

And here's Paul: "The GOP of old has grown stale and moss-covered," he said. "Our party is encumbered by an inconsistent approach to freedom. The new GOP, the GOP that will win again, will need to embrace liberty in both the economic and personal sphere. If we are going to have a Republican Party that can win, liberty needs to be the backbone of the GOP. We must have a message that is broad. Our vision must be broad. And that vision must be based on freedom."

Paul's words came back to me when I was cleaning out my inbox -- usually a chore, this time a treat -- and found a reprint of an article by James Buchanan in the March/April Cato Policy Report: "Saving the Soul of Classical Liberalism." Buchanan, a Nobel Prize-winning economist who died in January, said today's classical liberals lack "an animating principle, an ideal." They talk about "enlightened self-interest" and seek "scientific cover for advocacy" -- data tables conveying the large tax burden borne by the top 1 percent, for example -- when they would be better off presenting a vision.

What exactly is classical liberalism? Simply put, it's a belief in liberty; a belief that people have rights, and the proper role of government is to protect them. It's how today's conservatives view themselves. And classical liberalism is a lot different from today's liberalism, which finds new rights -- a right to health care, a job, an education -- as fashion dictates.

Buchanan said socialists have done a better job with their vision of "the pursuit of happiness in the aggregate." After all, "what else but the power of the socialist ideal can explain its longevity in Russia or even parts of Western Europe?"

Ronald Reagan's "shining city on a hill" expressed an ideal, a vision of what might be, Buchanan said. "Reagan could not himself solve the simultaneous equations of general equilibrium economics. His economics education was confined to undergraduate courses at Eureka College. But he carried with him a vision of a social order that might be. This vision was and is built on the central, and simple, notion that 'we can all be free.'"

It's not every day that a piece of mail in the inbox is so inspiring. Buchanan's article took me back to Paul's CPAC speech, Paul's CPAC speech to today's Republican Party, today's Republican Party to the realization of just how lacking it is in vision: at least the kind of vision Buchanan and Paul offer.

(Caroline Baum is a Bloomberg View columnist. Follow her on Twitter.)