On Wednesday, David Grusch, a former military intelligence officer, told a House Oversight subcommittee that all those stories you’ve read on the internet are true: The government has debris collected from crashed alien spacecraft. He also told the assembled lawmakers that federal retrieval teams have collected biological remains from alien bodies.

Grusch, who considers himself a whistleblower, claims he has interviewed dozens of people, several of whom claim to have been injured by UFOs, now officially known as unidentified anomalous phenomena, or UAPs. He also claimed the Pentagon has been working for years to collect and study crashed UAPs. That is a truly extraordinary claim, begging for extraordinary evidence.

But where is the evidence?

It’s MIA. Neither Grusch nor anyone else claiming to have knowledge of secret government UAP programs has ever been able to publicly produce convincing photos showing alien hardware splayed across the landscape. And remember, we’re not talking about a Cessna that plowed into a wheat field. We’re talking about, presumably, an alien interstellar rocket, capable of bridging trillions of miles of space, and sporting technology that is obviously alien.

The believers maintain that such photos exist but are being kept under wraps. For reasons that are always unclear, the critical evidence that would convince anyone of alien presence in our 'hood is classified. It can’t be made public. Note that this week’s star witness, Grusch, made this claim, too. 

This is an argument I have long viewed with skepticism. Society should not (and generally does not) accept scientific “discoveries” without any evidence. The cure for cancer cannot be classified. 

If there really was some physical evidence of visitation, thousands of scientists would be fighting one another to study it. And the government would want it studied. This has always been another big sticking point in the UAP conspiracy theory universe. What is the point of hiding extraterrestrial technology in a Nevada hangar? What would be the goal, at this point, of shutting out the scientific community. The information, technology and — importantly — wealth incentives here seem overwhelming.

Returning to the issue of visual evidence, there are thousands of satellites orbiting Earth. The majority sport cameras aimed downward. Actual alien craft in our airspace bigger than an office desk would likely be visible to satellites that — among other things — supply imagery to Google Earth. 

Hypothetically, a vast conspiracy to scrub such images could exist. And the American populace readily accepts conspiracy explanations.  Ever since the government’s disingenuous response to the 1947 discovery of crash debris near Roswell, New Mexico, the public has decided that the feds will never tell civilians the truth about visiting aliens. Not even dead ones, such as the crew of the spacecraft that reputedly pancaked into the desert that year. 

This theory is even prevalent in the halls of Congress, as evidenced by this week’s testimony. But I still strongly maintain that alien visitation is not something that could be kept secret. The size of such a secret is just too big.  

Nevertheless, a 2021 Gallup poll showed that more than 40 percent of Americans believe that some UFOs are alien spacecraft. And even the most conservative scientist can’t rigorously argue that it’s impossible for extraterrestrials to visit Earth. It doesn’t violate physics to go from one planet to another, even if that planet is in orbit around another star. Hard, yes. Impossible, no.

But admitting that aliens could be here is a far cry from claiming that they are here. And that they somehow manage to arrange things so that they’re exclusively met by government employees anxious to hide them.

And why is it that the aliens at least seem to invariably set their navigation hardware to visit America and not some other country that might not feel the need to keep these visitors under wraps? There is a kind of national hubris operating here: If extraterrestrial beings are going to come to Earth, they’re going to visit us!

So have the aliens arrived? From the standpoint of science, there’s still no good evidence for that, only an “argument from authority.” David Grusch says they’re here. But either he can’t prove it, or he won’t. Until he does, we should consider his stories to be just that: stories.

This article was originally published on www.msnbc.com.