"I don't know." "I don't remember." "I'm not familiar with that detail." "It's not my precise area." "I'm not familiar with that letter."These are quotes from the Internal Revenue Service officials who testified this week before the House and Senate. That is the authentic sound of stonewalling, and from the kind of people who run Washington in the modern age—smooth, highly credentialed and unaccountable. They're surrounded by legal and employment protections, they know how to parse a careful response, they know how to blur the essential point of a question in a blizzard of unconnected factoids. They came across as people arrogant enough to target Americans for abuse and harassment and think they'd get away with it.

So what did we learn the past week, and what are the essentials to keep in mind?

We learned the people who ran and run the IRS are not going to help Congress find out what happened in the IRS. We know we haven't gotten near the bottom of the political corruption of that agency. We do not know who ordered the targeting of conservative groups and individuals, or why, or exactly when it began. We don't know who executed the orders or directives. We do not know the full scope or extent of the scandal. We don't know, for instance, how many applicants for tax-exempt status were abused.

It is important to remember that there has never been an investigation of what happened in the IRS. There was an internal IRS audit, not an investigation, carried out by an inspector general, who was careful this week to note to the House what he'd done was NOT an investigation. He was tasked to come to conclusions on whether there had been wrongdoing at the agency. It was NOT his job to find out exactly why it happened, how and when the scandal began, who was involved, and how they operated.

A dead serious investigation is needed. The IRS has colorfully demonstrated that it cannot investigate itself. The Obama administration wants the FBI—which answers to Eric Holder's Justice Department—to investigate, but that would not be credible. The investigators of the IRS must be independent of the administration, or their conclusions will not be trustworthy.

An independent counsel, with all the powers of that office, is what we need.

If what happened at the IRS is not stopped now—if the internal corruption within it is not broken—it will never stop, and never be broken. The American people will never again be able to have the slightest confidence in the revenue-gathering arm of their government. And that, actually, would be tragic.