Mostly OT: The Impossible Fact
The saying "es kann nicht sein, was nicht sein darf" actually comes from the closing line of a poem by Christian Morgenstern. You can find the poem here, along with a congenial english translation:
https://www.babelmatrix.org/works/de/Morgenstern%2C_Christian-1871/Die_unmögliche_Tatsache/en/32691-The_Impossible_Fact