[Walter manages a nod.]

Yes.

... This can't be reversed, can it?

[It's barely a question.

Ways of thinking. People take them for granted, like the voice in the back of their heads - when it changes, does it mean something is wrong or just that you've grown, that you've learned something?

Only this isn't natural growth in the least - a reasonable precaution, yet utterly discontinuous from what had been before.]