Thinking is not just an activity, but a passion – a passion for that which is and remains to be thought.
Philosophy, as passion, is not – perhaps not – essentially mastery, but a vulnerability.
* * *
You could replace "philosophy", above, with "philology" – see Werner Hamacher's and Thomas Schestag's recent "theses" on philology – and, perhaps, "thinking" with "reading" and "thought" with "read" (that which "is and remains to be read" is "something" that certainly "is and remains to be thought", but some people might pretend that "that which is and remains to be thought" is not always something "to be read").
I am re-reading Octavio Paz's Children of the Mire, and the following in it:
Critical passion: excessive, impassioned love of criticism and its precise devices for disconstructions,* but also criticism in love with its object, ...
* "Disconstructions": I don't have the Spanish original at hand (while, on the other hand, the English translation is rather an English version, constituting Paz's Norton Lectures of 1972), but it would by no means be far-fetched to read "deconstructions", provided that we forget, for a moment, that deconstruction is not a device, let alone a set of "deconstructions" as a set of "devices".