Spirits were Arthur's favorite power manifestations, as they involved mutual trust between the user and the spiritual being. However, spirit users were as rare as phoenix feathers and unicorn horns.
Now that he thought about it, Trevor's ability to use a dark knight might have been a spirit in some way. However, abilities, traits, and spiritual contracts were hard to distinguish even by the users themselves.
An awakening back on earth could have been simply a spirit contract, while the user did it unaware. An ability could have been a human trait like those of Demis, only on the spiritual level rather than their genes.
There was an oblivious relation between summoners and spirits, so Arthur was sure that Jin was someone of high spiritual attainment.
Goal: TOP 200 POWER RANKING!