Donald Rumsfeld once categorized three forms of information: known knowns, known unknowns and unknown unknowns.

At today's House Intelligence Committee hearing on Russian interference in the 2016 presidential election, those categories were enlarged to include:

- Things we think we know but have no proof of, which has never stopped the American public before.


- Things we know that apparently are a big no-no for us to know.

- Things we would know if FBI Director James Comey would tell us, but he won't, except for confirming that the Russian investigation exists, which we already knew.

"Can you tell us who was in the room for the conversation?" asked one committee member, referring to a briefing that allegedly took place between President Donald Trump and FBI employees.

"I'm not going to confirm there was a conversation," Comey said.

"We all know that four of you went to Trump Tower, though," the committee member pressed.

"How do you know that?" Comey responded.

Do we - did we - I thought that someone said that - wait, what? No, you're the one who met with Russian ambassadors, in the conservatory, with the candlestick.

Two hours before the hearing was scheduled to start, there already was a line of citizens 60 or 70 deep waiting to get into the Longworth House Office Building's hearing room, seeking an explosive moment, a memorable exchange, the end of civilisation, a small piece of definitive truth and certainty.

"The conclusion that active measures were taken [by Russia] specifically to help President Trump's campaign . . . by early December, you already had that conclusion?" Congressman Michael Conaway asked Comey.

"Correct," Comey said. "That they wanted to hurt her, help him."

A few minutes later, the official presidential Twitter account posted: "The NSA and FBI tell Congress that Russia did not influence electoral process". That expresses a point that Trump has made before - but which was beside the point of the hearing.

What the intelligence agencies actually said was that there is no evidence that Russian agents had changed vote tallies in swing states, i.e. that the cast of The Americans did not put on a trench coat and drive to East Lansing to spirit away a ballot box.

Also, there was no wiretap.

It became clear that whatever known knowns those tourists, activists and aspirational democractic citizens were seeking - "I'm just glued to this," murmured a professor who said his sabbatical had been consumed by following the Russia investigation - it did not exist in Longworth.

Holding a public hearing provided an aura of transparency. A sense that now was the time to get to the bottom of things.

But in actuality, the hearing was "public" only in the sense that there was an audience present for all the times that Comey, and his counterpart, National Security Agency Director Michael Rogers, said that they could not divulge information in front of an audience.

"Please don't draw any conclusions from the fact that I may not be able to comment on certain topics," Comey told the committee at the beginning of the hearing. "I know speculating is part of human nature, but it really isn't fair to draw conclusions simply because I say that I can't comment."

It was an impossible request. With Comey and Rogers ducking and deflecting in the name of national security, the two men became receptacles for the bipartisan committee's respective biases, lambasted by leading questions that they were then unable to agree or disagree with.

Democrats focused on implying that Trump was what Hillary Clinton once memorably said he was: Russian President Vladimir Putin's puppet.

"Given Russian's long-standing desire to cultivate relations with influential US persons," asked Representative Terri Sewell, "isn't the American public right to be concerned about [former national security adviser Michael Flynn's] conduct, his failure to disclose that contact with the Russian ambassador, his attempts to cover it up and what looks like the White House's attempts to sweep this under the rug?"

"I can't comment," Comey replied.

Republicans focused on implying that the real concern was not the Russian investigation, but the fact that its supposedly top-secret contents were regularly leaked. By whom, they couldn't say - but they could strongly imply that it someone from the previous presidential administration. "Did you brief President Obama on any calls involving Michael Flynn?" asked Representative Trey Gowdy.

"I can't answer that," Comey said.

The end result allowed each questioner to claim victory, with roughly the same efficacy as if the roles of Comey and Rogers had been played by cardboard cutouts or well-behaved labradoodles.

But what are you going to do? Russia is apparently our official adversary again, was the message behind all of the back-and-forths - the terrifying spectre of another Cold War, another nuclear arms race hanging over the congressional hearing room.

And this was democracy, happening in public, laying bare all the sordid truths we wish we knew, but don't, and won't, and would probably forget anyway.