TheoryInterdimensional hypothesis IDH

Jacques Vallée’s Passport to Magonia (1969) is the canonical statement. Vallée — a French-American astrophysicist trained under Hynek at Northwestern, principal investigator on the ARPANET-era Network Information Center — surveyed centuries of fairy lore, Marian apparitions, airship sightings, and contemporary UFO close encounters and observed that the structural features are stable while the surface presentation changes to match the era’s expectations. Fairies become airships become flying saucers become drones.

The hypothesis takes the strangeness of the encounters as signal rather than noise. The features the ETH brackets as embarrassment — telepathy, missing time, contradictory or absurd messages from occupants, the simultaneous presence and absence of physical traces, the tendency of the phenomenon to evade systematic study while remaining persistent enough to keep generating witnesses — are, on the IDH, the actual structure of the thing. John Keel’s The Mothman Prophecies (1975) and Operation Trojan Horse (1970) advanced a darker version: the phenomenon is “ultraterrestrial,” interacts with human consciousness, and is not necessarily benign.

What the IDH predicts: physical traces will be inconsistent and partial. Witnesses will report perceptual and cognitive anomalies. The phenomenon will appear most clearly to single witnesses or small groups, less clearly to instrumented arrays. Hardware will not be recoverable in a way that yields a clean propulsion story. The phenomenon’s surface presentation will track the surrounding culture’s technological imagination.

Where the IDH differs from neighbors: from the ETH in rejecting the physical-spacecraft model; from the psychosocial hypothesis in insisting that something with its own agency is doing the contacting; from the Jungian-archetype hypothesis in granting the contacting agency external reality rather than treating it as a projection of the collective unconscious; from the demonic hypothesis in declining to identify the agency with any particular theological framework.

Vallée himself has said that he considers the IDH a research program, not a settled answer. Dimensions (1988), Confrontations (1990), and Revelations (1991) form the trilogy in which he works out the implications.