The Oz Factor

Aliens

Theories.
Defense.
Bibliography.

Theory: They are hypnopompic and hypnagogic hallucinations.

Pro:

People often report experiencing abduction phenomena just as they are falling asleep or just as they are awaking (ergo in hypnagogic and hypnopompic states, respectively).
They also report an inability to move their limbs, an apt description of the sleep paralysis that ordinarily accompanies these states in order to prevent people from acting out their dreams.
Witnesses often describe seeing shadowing figures on the periphery of their vision, again a manifestation of these states of consciousness.
People observing the person experiencing supposed abduction phenomena do not see creatures standing at their friends bedside

Con:

People report seeing aliens when they are in fairly alert states (hiking, driving, etc.)
They are also sometimes seen by more than one person at a time.
People can also have physical evidence or damage, though it is rare.
Extremely rarely, photographs of aliens have been taken.

Theory: Aliens are physical Jungian archetypes/faeries.

Pro:

Psychics and "sensitive people" are often more apt to experience alien phenomena

Con:

Theory: Aliens are creatures from another planet.

Pro:

UFOs are certainly beyond human capability to produce.
They also appear to have evolved in a very different climate (more sunlight, lower gravity).
There means of communication is reported to be vastly different than almost all human languages (clicks and whirs. When speaking to humans, it is through telepathy).

Con:

Given the distance these beings would have to travel and the technological capabilities inherent in interstellar space flight, their behavior and purported medical experiments make very little sense.
Different "breeds" of aliens are reported in different part of the world.
- North Americans claim to have seen Grays.
- South Americans usually report Chupacabras (greenish, vicious, feral, spiked versions of Grays).
- Europeans tend to see Icelandic humanoids.
If the fossil record and prior art are any indication, these being have been visiting us since we were advanced enough to note their existence. Beings from another world would likely have made some move ten of thousands of years ago.

Theory: Aliens are time traveling humans from the distant future.

Pro:

Their technology is ostensibly beyond our current abilities, but tends to be within our conception.
UFOs tend to be seen more often around tumultuous social events, which would be of great interest to people from the future.
This would also justify their interest in Earth.
This would explain why the aliens purportedly do genetics experiments, rape women, and create cross-breeds.

Con:

While it is possible (and optimistic) that human time travelers would look like the six foot tall, white-blond humanoids seen in Europe, it is unlikely humanity would have evolved into withered limbed, gray skinned entities with bulbous head our necks can barely support.
They are not doing a very good job concealing their existence and, indeed, have influenced and altered society with their presence. This would be a catastrophically bad idea for a time traveler, as it could create a paradox.

Theory: Aliens are hyper evolved dolphins from the future.

Pro:

Aliens are said to speak through clicks and whirs, like dolphins can.
They ability to paralyze humans is apparently akin to dolphins ability to debilitate sharks with sonar.

Con:

What would cause dolphins to evolve back out of the sea and into what we call aliens?

While one can point out the structures on a whale that evolved from what amounted to a kind of wolf, it is much, much harder to diagram how what structures on Grays are from whales.

Defense

Break the thrall: If you are in an abduction situation and you begin to hear "Please be calm. We won't hurt you." remember that they are lying to you. If a stranger came up to you and wanted you to come back to their apartment so they could rape you, would you listen to them if they told you to be calm? Of course not. If you start screaming and fighting them, they are going to go away. They don't want any trouble. They aren't just picking people off the street because they need to use that thrall. They need you to give in and not fight back.
Fight: Look at pictures of the Grays. Thin limbed. Bulbous in places. No claws or even teeth? Once you have broken their complacency thrall, remember that you have the distinct physical advantage. Just grab one and shake it vigorously. It will get the idea… or a broken neck.
Appeal to a higher force: I don't pretend to fully understand this, but praying or doing a spell with conviction tend to frighten them off. Perhaps it is the stronger force of will displayed in these acts. As they need you to be weak willed and complacent, this gives you a far better chance against them.