Symbolism

Systema Sephirotica - Tree of Life :

If one analyses the stages in the Tree of Life, it can be found, that each main character in Evangelion parallels a single sephira. Each shows all the virtues, vices, illusions and obligations of their parallel sephira on the Tree of Life, and each either succeeds or fails to achieve fulfillment based on that sephira.
Shinji for instance can be seen as Yesod, because he rather does nothing than to do something wrong, he always tries to play it safe, and when he acts, he does so in a robotic, superficial way.
Asuka on the other hand is impulsive, proud and, if the outer shell is removed, hollow. Thus she can be seen as Tipereth. Such a similarity could be found for each major character, as will be described in the according section.