From the transcript of an interview with Fraulein Liebert:

I've often heard it told that twins, even as infants, develop their own private language, which only the two of them can understand. This is a fallacy...as far as I'm aware. My...my brother and I, we did not speak the same language. That did not stop us from comprehending each other, as much as I would like to deny it. A part of an individual can remain unknowable even to himself, but this barrier to communication does not necessarily split his essential unity as a person. It is very important to remember that. A person is always whole, no matter how fragmented he seems to himself or to others. Like a hard-boiled egg whose shell is cracked but continuous.

My brother...Johann...he would not have agreed with me. To him, I was neither a separate entity or an appendage of himself. He thought of me as his doppelganger. A mirror image, but not a perfect reflection: distorted, flawed. Or rather he thought of himself as the distorted one. We could not coexist, faced with this other who was not-other. But he loved me, I know, in his own way. He could not bring himself to eliminate me, whom he thought of as the truer image, and perhaps that is why he did what he did.

[long silence]

On the other hand, I was fully prepared to kill him myself. If I am to be honest, there was a point where I was able to do it. Psychologically, spiritually, mentally.

Inside me, there is a murderer. Johann and I never shared a language, but those were the last words he left impressed on my heart.

[end of interview]