What Would Taxes Look Like if Arlen Specter Were King?

Via Matt Yglesias, I see that soon-to-be Democrat Arlen Specter supports a flat tax. Indeed, he has introduced flat tax legislation since 1995 -- often energetically, and with Grover Norquist at his side. "Flat tax" is a bit of a slippery term -- after all, Rahm Emanuel and Ron Wyden once introduced a flat tax -- but the Specter version isn't especially complicated. It would be a 20% tax on individual and business income, with a few deductions kept around for good measure. What would that look like? Why, it would look a little something like this:

I like the progressive income tax, so I find the flat tax unappealing for moral reasons. But I also find it slightly bizarre that Specter believes the main recommendation for this tax is that it will "dramatically simplify the payment of taxes." Sure, the tax code is complicated and should be made simpler. But that's an ancillary concern. The point of the tax code is to raise revenue efficiently and pursue a variety of desirable social goals (which you can bundle under the heading of fairness). Making sure taxpayers can mail a postcard to the IRS makes a triviality into a fetish.