A: A existentialist who's afraid of the void.
B: A phenomenologist with a fear of the unknown.
C: A hermeneuticist who's lost their keys.
D: A nihilist who's just giving up.
According to Jean-Paul Sartre, a philosopher in the dark is called a "Being-for-itself-in-the-dark".
Or so he says, when he's not being too existential about it.
But seriously, if a philosopher is in the dark, they're just lost.
Like that one philosopher who got stuck in a revolving door for hours.
Read about the time a philosopher got stuck in a revolving door