I'm watching an online class on YouTube about Nietzsche, and there was this phrase. In which book Nietzsche says "es denkt in mir"?
F. W. J. von Schelling, On the History of Modern Philosophy (Zur Geschichte der neueren Philosophie, probably 1833–4), English tranls., page 48 :
It thinks in me, thinking goes on in me, it is the pure fact, in the same way as I can say with equal justification : "I dreamed", and "It dreamed in me". [See German text.]
Nietzsche discusse "It thinks" into Beyond Good and Evil (1886), § 17.