Deleuze commented in a letter to one of his translators that his purpose in writing What is Philosophy? was to address "the problem of absolute immanence" and to explain why he considered Baruch Spinoza the "prince of philosophers."
Deleuze kommenterede i et brev til en af sine oversættere at han i Hvad er filosofi? forsøgte at vende tilbage til "problemet med absolut immanens" og for at sige hvorfor Baruch Spinoza for ham er "filosoffernes prins".