Sorry for wasting your time and using the ideas of the first person who came with this theory before me, if that person happens to exist.
Christian Shepard died in Australia. Jack, went to Australia to bring him to home and got on the flight oceanic815. The coffin was in the plane, and the plane crashed on the island because of Desmond as revealed in season 2 final. When Desmond pushed the button later that he supposed to, audience saw hyerographic (don't know how to spell) symbols instead of the time left for pushing the button. The electromagnetism caused by "the incident" wasn't discharged and the plane was affected and as a result, it crashed on the island. In 4x05 Faraday stated to Desmond as Elois didn't traveled in time, but its consciousness went back in time. I think at the time of crash , Christian's body exposed high amount of electromagnetism and his consciousness started to time traveling just like Desmond in 4x05. Also -I'm not sure about which ep exactly- Faraday said that the helicopter must follow the exact bearing. If the exact bearing is not followed, it's consequences will be "unpredic! table". SO, the plane didn't crash in the exact bearing Faraday calculated, so the electromagnetism and the wrong bearing followed by the plane during the crash caused a "dead" brain to travel in back. When the mind traveled back in time his body somehow in someway resurrected. These two events are the mystery behind Christian's being on the island. But there are many questions rise up on this theory by now in my mind like Why didn't he explained everything to his son or daughter. My guess would be , He maybe in shock or he could be "special" ( I have no idea what the heck that word would mean) and he serves to the island...
But maybe this unpredictable consequences of both electromagnetism and plane's crashes wrong bearing could send his mind back in different past dates.
His consciousness is not in a stable time. This may also be a weak explanation for why does he act weird.
I didn't like this theory's end but it has some points worth to share..
Please add or correct anything you want
cheers
Theory by tatarramazan
Christian Shepard died in Australia. Jack, went to Australia to bring him to home and got on the flight oceanic815. The coffin was in the plane, and the plane crashed on the island because of Desmond as revealed in season 2 final. When Desmond pushed the button later that he supposed to, audience saw hyerographic (don't know how to spell) symbols instead of the time left for pushing the button. The electromagnetism caused by "the incident" wasn't discharged and the plane was affected and as a result, it crashed on the island. In 4x05 Faraday stated to Desmond as Elois didn't traveled in time, but its consciousness went back in time. I think at the time of crash , Christian's body exposed high amount of electromagnetism and his consciousness started to time traveling just like Desmond in 4x05. Also -I'm not sure about which ep exactly- Faraday said that the helicopter must follow the exact bearing. If the exact bearing is not followed, it's consequences will be "unpredic! table". SO, the plane didn't crash in the exact bearing Faraday calculated, so the electromagnetism and the wrong bearing followed by the plane during the crash caused a "dead" brain to travel in back. When the mind traveled back in time his body somehow in someway resurrected. These two events are the mystery behind Christian's being on the island. But there are many questions rise up on this theory by now in my mind like Why didn't he explained everything to his son or daughter. My guess would be , He maybe in shock or he could be "special" ( I have no idea what the heck that word would mean) and he serves to the island...
But maybe this unpredictable consequences of both electromagnetism and plane's crashes wrong bearing could send his mind back in different past dates.
His consciousness is not in a stable time. This may also be a weak explanation for why does he act weird.
I didn't like this theory's end but it has some points worth to share..
Please add or correct anything you want
cheers
Theory by tatarramazan