This is my first theory. This is JUST A THEORY...stay calm, and critique it, hate it, love it, rip it to shreds, or ignore it! It's all just in fun!
Avatar-“a manifestation of a deity or released soul in bodily form on Earth” (or another planet/moon, haha)
AVATAR is about Entu, Toruk Makto. Jake Sully is Entu reincarnated.
For those who don't know who Entu is, he is the first (and only, in my opinion)Toruk Makto(a title given to a Na’vi who successfully rides a great Leonopteryx) and was born of the Omaticaya Clan in 852 b.c. Toruk: The First Flight describes him as a pure soul who rises among the clans to ride Toruk and save the Na’vi from a terrible fate. Entu is a deity, or hence the name of the movie, an Avatar who would go on being reborn 4 more times to help Eywa in her times of need.
Now I know in the movie Norm says “Eywa is the Na’vi deity, their goddess made up of all living things; everything they know.”...All living things. Everything they know. Sounds like Pandora. Which makes me believe Eywa is Pandora, not a deity or goddess. Eywa is a mother. She created her children(everything on her from the Na’vi to plant life) and unlike Gaia(Earth) our mother, Eywa’s children did not kill her, she is alive and conscious(The Pandoran Neural Network) caring for her children and keeping herself in perfect balance. In the words of Sully “They killed their mother, and now they're going to do the same here.”
You're probably wondering why the hell would Eywa send Entu’s soul to Earth?
I believe the Universe has a similar neural network to The Pandoran Neural Network that allows the Universe to “communicate” to its children whose neural networks still function. The Universe knew about the humans and the outcome they would have going to this moon they called Pandora, and so Entu’s soul went to Earth. Think of it as getting to know the enemy.
With all that said on to Jake Sully. Sully means “damage the purity or integrity of”. Entu’s soul became sullied from living life on Earth as a human. Mo’at, Neytiri’s mother and shaman of the Omaticaya takes a “blood sample” tastes it and then tells Sully/Entu to “learn our ways, than your insanity may be cured”. This “insanity” she speaks of is the sullied parts of Entu from being human. The movie is him slowly realizing who he is(Entu,Toruk Makto), where he belongs(Eywa not Earth), and getting his purity or sanity back(becoming Na’vi and saving Eywa and her children from the humans) which allows him to remain in his true Na’vi form and remain on Eywa.
Here are the rest of the clues for this theory of Jake Sully being Entu, Toruk Makto:
At the beginning of the movie Sully mentions “dreams” of flying while in the hospital. I believe these are Entu’s memories of previous lives on Eywa.
He conveniently had an identical twin brother, who was conveniently a scientist, who weirdly out of the thousands of scientists from Earth just so happened to CONVENIENTLY work on Pandora/Eywa and CONVENIENTLY was killed. Hmmm.
When Sully and Norm connect to their Avatars together, we can clearly tell Sully seems used to his Na’vi body right away. He even has the biggest grin on his face when he answers Dr. Patel saying “you're not used to your avatar body!” with a “this is great!” Then he proceeds to run around outside like its nothing, like he was always a Na’vi, which he was.
Neytiri is stopped when going to kill Sully by Eywa herself through the woodsprites from the Tree of Souls, which Neytiri says are “very pure spirits”, and then later sending the pure spirits to cover Sully, in my opinion showing a sign that he is Entu.
Shortly after Neytiri and Sully hunt a top Ikran, the Leonopteryx(Toruk) goes right for Sully, like he is challenging him just like Neytiri mentioned Ikran’s do when choosing their rider, and to me Toruk is just an over sized Ikran. Entu made Tsaheylu years ago, i believe intertwining their souls and destinies.
And than of course the obvious, Sully makes Tsaheylu, receives the title of Toruk Makto, brings the clans together in a time of great sorrow, and defeats the humans with a little help from his moon mom Eywa! XD
So that's it, AVATAR is about Entu, the first and only Na’vi to ever receive the title Toruk Makto making himself a legend and deity in the process, and being reincarnated 4 times after in times of great sorrows.