The following text is transcribed from the ADV dub of Neon Genesis Evangelion episode 25, and provides a brief summary of the Human Instrumentality Project...
Shinji Ikari: What... What feeling is this? I think I've experienced this sensation before... It's as though my physical form was disappearing. It feels... agreeable... As though my existence is spreading itself out to cover the entirety of existence...
Gendou Ikari: Incorrect. It is not a return to nothingness. It is merely a return to the state of beginning. It is no less than a return to the primal womb that we lost so long ago. Souls and minds will become one, attaining eternal balance. The final goal is nothing more than that.
Misato Katsuragi: And that's Instrumentality.
Ritsuko Akagi: Yes. There is an emptiness at the very core of our souls. A fundamental incompleteness that has haunted all beings since the very first thought.
Ritsuko Akagi: On a primal level, Man has always been aware of the darkness that resides at the core of his mind. We have sought to escape from this void and the fear it causes, as all Man's accomplishments were made in the hope of filling it.