is the 16th Amendment. As long as it's on the books, the odds are that within a few years, we'd end up with both a consumption tax and an income tax. All it would take is for a severe budget crunch to get Congress to pass a "temporary" income tax. Few things made by man are more permanent than a temporary tax, as illustrated by the "temporary" tax on long distance phone calls that was passed in 1896 to pay for the Spanish-American War that's still on the books.

In the end, I'd greatly prefer either a flat tax or a consumption tax over the monstrosity that is our current tax code. I just have some reservations about leaving the 16th Amendment on the books. Given that over 40 states have their own income tax, the chances of repealing the 16th Amendment are damned close to zero.