Right after Sept. 11 last year, Americans held hands so that no one pointed fingers.

Now, one year later, Washington resumes the politics of blamesmanship. The Congress' probe of Sept. 11 peeked out from behind closed doors last week and triggered angry reactions this week. Reversing course, the Bush administration now favors an independent commission to report on "what went wrong."

Key for this commission, and all Americans, to understand, if not unlock, many "intelligence failures," is the fundamental distinction between a secret and a mystery.

A secret is something knowable, but something known only to a few insiders. Like all aspects of human existence, Shakespeare shows this clearest. His hunchback, Richard III, devised a plan to become king and was evil enough to murder all those in his path. This secret was shared with his henchman.

In contrast, a mystery is something simply unknowable. MacBeth could become king by murdering the current king, Duncan. But whether this would happen was uncertain to Lady MacBeth -- indeed, even to MacBeth himself -- since he didn't know if he could commit murder.

Intelligence agencies -- the CIA, FBI, NSA, and others in the alphabet soup of Washington bureaucracy -- can (and should) be blamed for not uncovering secrets. But they should never be blamed for failing to unlock mysteries.

Take two of the biggest "intelligence failures" of the past quarter-century, shocking events in Iran and the Soviet Union.

Right after the fall of the Shah of Iran in 1979, President Jimmy Carter dashed off a hand-written memo to his CIA director complaining of this grave intelligence failure.

Yet President Carter's pique was a bum rap.

For there was no secret to uncover. The Ayatollah Khomeini's agitating for the Shah's overthrow was all done in plain sight. But it was a mystery how Iranians would react to Khomeini's sermons.

Neither the Ayatollah nor the Shah could know it. So the CIA couldn't know it, either.

A decade later came the startling collapse of the Soviet Union. How could so momentous an event surprise our $20-billion-a-year intelligence empire?

Mikhail Gorbachev's shaking up the communist system through perestroika and glasnost was out there for everyone to see. And it wasn't any secret that his program would unleash unpredictable forces.

But it was a mystery how it all would play out. Gorbachev himself -- and, most poignantly, even his KGB -- didn't know. So how could the CIA?

Take the most crucial intelligence issue of today. Saddam Hussein's arsenal of chemical and biological weapons -- and how close he is to getting his hands on nuclear weapons. These are secrets. These are knowable.

We'll soon find out if the U.N. inspectors can uncover such secrets. Any chance of success would be predicated on some essential elements. The U.N. inspectors must be:

-- heavily armed,

-- able to go anywhere, at any time,

--able to take Iraqi informers out of the country, with their families, to reveal where Saddam's most dangerous weapons facilities are hidden.

Absent these three, the secrets will remain with Saddam and a small number of his hooligans.

What Saddam will do with his vast arsenal, however, is a mystery. It's quite impossible for U.N. inspectors, or the CIA, to predict the actions of someone who hasn't made up his own mind.

Likewise, the plan of the Sept. 11 atrocities was a secret -- known to Usama bin Laden and a few top lieutenants. But surely some aspects of  Sept. 11 -- as in all intelligence issues -- are mysteries.

The new commission can point fingers at not detecting or connecting secrets. But it should be lenient on intelligence officers for not knowing unknowable mysteries in life.

Kenneth Adelman is a frequent guest commentator on Fox News, was assistant to U.S. Defense Secretary Donald Rumsfeld from 1975 to 1977 and, under President Ronald Reagan, U.N. ambassador and arms-control director. Mr. Adelman is now co-host of TechCentralStation.com.