A Field Guide to the Visitors: How We Classify the Unknown

The first serious framework came from an astronomer. J. Allen Hynek served as the United States Air Force's scientific consultant on Project Blue Book, and in his 1972 book The UFO Experience he set out a three-level scale for the cases that mattered most, the close ones. A Close Encounter of the First Kind, CE-1, is a close visual observation, within roughly 150 meters, of an object that leaves no lasting mark. A Close Encounter of the Second Kind, CE-2, leaves physical evidence, scorched ground, a stalled engine, electromagnetic interference, or a physiological effect on a witness. A Close Encounter of the Third Kind, CE-3, is an observation of occupants or entities associated with the object, the rung most people picture when they picture a close encounter.

The scale most people know has five rungs, not three, and the last two are not Hynek's. A Close Encounter of the Fourth Kind, CE-4, an abduction or unwilling transport, and of the Fifth Kind, CE-5, deliberate human-initiated contact, a rung credited to Steven Greer, were added later by other ufologists. Hynek drew the ladder to three. Everything above CE-3 is a later bolt-on, and it is worth keeping that seam visible, because CE-4 is where the entire abduction literature lives, and that literature has its own dossier in this wing. Here, CE-4 is one rung, and nothing more.

One principle ran underneath all of it. Hynek, trained to distrust the lone anecdote, weighted instrumental and multi-witness confirmation above single-witness testimony. A radar return backing a pilot's account beat a solitary report from a field every time. That instinct, evidence over story, is the thread that runs from his 1972 ladder straight to the government office that would take up the same problem half a century later.

Where Hynek built a ladder, Jacques Vallee built a grid, and he built it for databases. Vallee wanted a classification a machine could actually store and query, so he split the phenomenon across two parallel axes. The Anomaly axis runs from AN1, an unusual light or an unexplained aerial explosion, to AN2, a physical craft with a definite shape, then AN3, a craft with associated beings, AN4, a witness experiencing altered reality or distorted time, and AN5, an anomaly that causes permanent injury or physiological change. A parallel Maneuver axis, MA1 through MA5, records those same five severities observed at a distance rather than up close. Vallee set the system out with Chris Aubeck in the 2010 book Wonders in the Sky.

And it caught on where it counted. Vallee's AN/MA scheme was adopted by SOBEPS, CUFOS, and other international UFO-research organizations, the groups that needed to file thousands of cases in a form a later analyst, or a computer, could sort. This is the quiet hinge of the whole story. Classification stopped being about awe and started being about data structure.

For decades this was hobbyist and academic work. Then the government took it back. In July 2022 the Department of Defense stood up the All-domain Anomaly Resolution Office, AARO, and gave it a framework of its own, three axes this time. The Domain axis asks where the thing was: airborne, transmedium, submerged, in space, or ground-based. The Sensor axis asks how well it was caught: visual only, single-sensor, multi-sensor, or radar-visual. And the Assessment axis asks the only question that finally matters, whether the event is identified, short on data, or genuinely anomalous. It is Hynek's instinct, evidence above anecdote, rebuilt as a standing bureaucratic instrument.

The office has never been short of material to sort. AARO's first director, Sean Kirkpatrick, has cited monthly UAP report volumes in the range of dozens to roughly a hundred, an inflow steady enough to turn classification from a philosophical exercise into an operational one. The precise monthly figure is hard to tie to a single public source; what is well documented is the order of magnitude, dozens of fresh reports a month.

In 2023 the classification tradition reached a place it had never been, federal law itself. The National Defense Authorization Act for fiscal year 2024, Public Law 118-31, in Sections 1841 through 1843, put the term 'non-human intelligence' into United States law for the first time. And it did something a taxonomist would recognize instantly. It split the category. The enacted definitions distinguish biological non-human intelligence from non-biological non-human intelligence, a living thing from a made thing, and treat the two as legally different kinds. The same law ordered federal agencies to review, organize, and transfer their records on unidentified anomalous phenomena, technologies of unknown origin, and non-human intelligence to the National Archives, with a deadline of October 20, 2024.

It is worth being exact about what did and did not become law, because the research file behind this article is not. The original bipartisan Schumer-Rounds proposal, the UAP Disclosure Act, reached much further. It would have asserted federal eminent domain over privately held recovered materials, and it would have created an independent UAP Records Review Board with the power to force disclosure. Both of those provisions were stripped out in negotiation before the bill was signed. Neither is law. What actually survived is narrower, and for a classification article it is the more interesting part anyway, the records mandate and the two new legal words. No eminent-domain seizure, no review board, just a filing deadline and a definition.

That biological-versus-non-biological line did not appear from nowhere. Months before the NDAA was signed, on July 26, 2023, a former intelligence officer named David Grusch sat before the House Oversight Committee and testified, under oath, that the United States government possesses 'intact and partially intact vehicles of non-human origin' and 'non-human biologics.' Grusch was not a fringe voice. He was a GS-15 who had worked with the National Geospatial-Intelligence Agency and the National Reconnaissance Office. And notice the shape of what he swore. He separated recovered vehicles from recovered biology, the machine from the organism, the very split that Congress would soon recognize in law. His testimony spoke the government's emerging taxonomy fluently.

Now the discipline the subject demands. Grusch's testimony is sworn, and it is legally consequential. A witness stating these things to Congress is not the same as a rumor traded online. But it is testimony, not evidence anyone can hold. Grusch said plainly, in the same hearing, that he has personally seen neither a craft nor biological remains; his account rests on what he was told by more than forty people he interviewed over four years. The Pentagon has said it cannot substantiate the claims. So this article puts his testimony exactly where the evidence leaves it, not proven and not debunked, a serious sworn statement still waiting on the physical proof that would settle it either way.

His path to that witness table was itself official. Grusch filed a whistleblower complaint in May 2022, and in July 2022 the Intelligence Community Inspector General found it 'credible and urgent,' the statutory trigger that sent a summary to the Director of National Intelligence and to the Senate and House intelligence committees. Whatever one makes of the content, the machinery that carried it was the real apparatus of oversight, not a stage.

Every system so far sorts behavior, sensors, and legal categories. Not one of them answers the question underneath all of them. If something really is behind the wheel, what kind of thing is it? Here the ground drops from documented fact to hypothesis, and a handful of serious ideas compete for the space. The research file grades them all Tier 2, credible, argued by real thinkers, and none of them proven. Each also carries its own built-in weakness, which is the honest column of the table below.

That last row is not idle speculation dressed up as science. It is the same distinction the FY2024 NDAA wrote into statute and the same one Grusch drew under oath. The 'non-biological' category exists in federal law precisely because some of the accounts describe a made thing rather than a born one, and, as the research file notes, an alien organism and an alien machine would demand completely different tools to study.

Past the credible hypotheses the footing turns soft, and the research file marks the next set Tier 3, speculative, ideas worth naming and not worth betting on. One holds that several kinds of intelligence could be operating at once, extraterrestrial and ultraterrestrial and artificial together, which would neatly explain why the reports refuse to describe a single consistent thing. Another holds that some intelligences may not be physical at all, existing as consciousness patterns or information structures with no material body, an idea that shades toward panpsychism and straight out of anything a sensor could catch.

Two more sit at the same tier. Drawing on Diana Pasulka's 2019 work, some researchers map the modern entities onto the old ones, angels, demons, jinn, fae, and argue the phenomenon is one persistent reality retold through each era's dominant cosmology, the same visitor under a new name every few centuries. And Michael Masters has proposed that the visitors may simply be us, future humans or temporal travelers, which would account for their reported humanoid shape and their reported interest in human genetics. Elegant, unfalsifiable, and firmly Tier 3.

And now the part the folklore gets backwards, stated at the tier the research file assigns it, Tier 4, dubious. The comprehensive species catalog, the familiar one with Greys and Nordics and Reptilians and Arcturians and Pleiadians, each fitted with a defined home planet and a temperament, has no verifiable basis. None. It is the single most confidently asserted body of 'knowledge' in this entire subject, and it is the least supported one. That is not a skeptic's verdict imported from outside. It is the plain assessment of the same research file that supplies everything else on this page.

The same verdict lands on the treaties. Claims that world governments signed formal diplomatic agreements with named alien species, technology traded for access, sit at Tier 4 with no declassified support of any kind. A dramatic story, and an empty folder.

And the grandest claim of all, that a complete, validated scientific taxonomy of alien species already exists and is merely being withheld from the public, outruns anything even the strongest whistleblower has said. Look back at Grusch. Under oath, he described recovered vehicles and recovered biologics. He did not describe a finished catalog of species with names and origins. The boldest sworn testimony in this entire wing stops at exactly the point where the folklore starts.