So even expenditures for the common good may be unjust, if they "drain and exhaust" wealth; if they are premised on the denial of the natural right to own the fruit of one's labor; or if the state "deprives" the private owner rather than assist and supplement, in the manner of subsidiarity.

Although there can be gray areas, one may also expect that there are lines which, when crossed, clearly signal excessive taxation. The peasants in Pharaoh's Egypt paid a rent of 30 percent. Historians tell us that serfs in medieval Europe paid the manor lord about 25 percent and maybe 10 percent more in tithes to the Church. These burdens do not look light to us now. The marginal tax rate in the U.S. is currently about 50 percent: that is, earn an extra dollar, and after combined taxes (including FICA collections), the worker gets to keep only half.

Someone might say that a reasonable guide to the justness of a tax system is whether it strikes a generous and fair people as just. But in order to discover this, make it so that they appreciate concretely what that system really is. Instead of automatic payroll deductions, require people to go to a tax office and pay their tax in cold cash--so that it becomes very clear what good things, such as education or home improvement, they are not spending this money on. Then, instead of treating their tax payments as all fungible, keep each individual's payment nominally in a "packet," and follow its use, so that each person can go to the internet and find out exactly how his "packet" of taxes was spent--just as for some relief agencies you can know the name of the child your donation helped.

People could then easily see whether the share they were paying was "fair."

Michael Pakaluk is professor and chairman of philosophy at Ave Maria University and the author (with Mark Cheffers) of "Accounting Ethics."