On Friedrich Nietzsche's The Gay Science (1882, with book 5 added 1887).
What is wisdom? Nietzsche gives us an updated take on the Socratic project of challenging your most deeply held beliefs. Challenge not just your belief in God ("God is dead!") but uncover all your habits of thinking in terms of the divine. Question the motives behind relentless inquiry: the "will to truth." Realize how little of your life is actually a matter of conscious reflection, and the consequent limits on self-knowledge. The very act of systematization in philosophy overestimates what we can know; instead, we need a "gay" (in the sense of cheerful, carefree, and subversive) science (in the sense of organized knowledge; this is not about modern experimental science) that chases after fleeting insights and is able to question, i.e. laugh at, the pretensions of its own activity. This is the position from which one can then artistically create one's own character and one's values, and this "creation" is not whimsical in the sense of arbitrary, but is a matter of rigorous and careful discernment, an exercise of one's "intellectual conscience." Hear Mark, Wes, and Dylan frolic through this field of aphorisms and short essays.
End song: "Take a Hike," by Mark Lint and Stevie P. Read about it.