Imagine that God were to appear on Earth for the unlikely purpose of settling, once and for all, our disputes over economic policy. And suppose that, to my enormous surprise, he announced that every empirical claim advanced by conservatives was correct. Cutting taxes produces such great economic growth that even the poor benefit. Privatizing or eliminating social programs like Medicare and Social Security will cause the elderly to save more money and enjoy higher living standards. Slashing regulations, by eliminating unintended side effects, actually does a better job helping those whom the regulations were intended to help than the regulations themselves. Suppose that God presented these conclusions so convincingly--if his stature alone did not suffice--that everybody immediately accepted them as truth.

How would liberals respond? No doubt by rethinking and abandoning nearly all their long-held positions. Liberalism, after all, claims to produce certain outcomes: more prosperity and security, especially for the poor and middle classes; a cleaner environment; safer foods and drugs; and so on. If it were proved beyond a doubt that liberal policies fail to produce those outcomes--or even, as conservatives often claim, that such policies hurt their intended beneficiaries--then their rationale would disappear. It may be hard to imagine liberals advocating capital gains tax cuts as a way to lift up the working stiff. But that's just because there's no evidence to show they do. If the evidence were to change, so would the liberal mindset. The point is that liberalism has no justification other than the belief that liberal policies produce beneficial outcomes.

Now imagine the opposite were to happen. God appears in order to affirm liberal precepts: Current tax levels barely affect economic incentives, social programs provide tremendous economic security at modest cost to growth, and most regulations achieve their intended effects without producing undue distortions. Would economic conservatives likewise abandon their views? Some certainly would, but a great many would not. Economic conservatism, unlike liberalism, would survive having all its empirical underpinnings knocked out from beneath it.

And not because conservatives are necessarily more stubborn. (Indeed, on an individual level, liberals may well be just as stubborn as conservatives.) Rather, conservatism, unlike liberalism, overlays a deeper set of philosophical principles. Conservatives believe that big government impinges upon freedom. They may also believe that big government imposes large costs on the economy. But, for a true conservative, whatever ends they think smaller government may bring about--greater prosperity, economic mobility for the non-rich--are almost beside the point. As Milton Friedman wrote, "[F]reedom in economic arrangements is itself a component of freedom broadly understood, so economic freedom is an end in itself."

We're accustomed to thinking of liberalism and conservatism as parallel ideologies, with conservatives preferring less government and liberals preferring more. The equivalency breaks down, though, when you consider that liberals never claim that increasing the size of government is an end in itself. Liberals only support larger government if they have some reason to believe that it will lead to material improvement in people's lives. Conservatives also want material improvement in people's lives, of course, but proving that their policies can produce such an outcome is a luxury, not a necessity.