The fundamental question of metaphysics.

The question we have identified as first in rank—"Why are there beings at all instead of nothing?"—is thus the fundamental question of metaphysics. Metaphysics stands as the name for the center and core that determines all philosophy.

There Heidegger inserts a note into the lecture's text:

[For this introduction, we have intentionally presented all this in a cursory and thus basically ambiguous way.

Ending, 2 pages later:

The fundamental question of the lecture course is of a different kind than the guiding question of metaphysics. Taking Being and Time as its point of departure, the lecture course asks about the "disclosedness of Being" (Being and Time, pp. 21 f. and 37 f.). Disclosedness means: the openedness of what the oblivion of Being closes off and conceals. Through this questioning, too, light first falls on the essence of metaphysics, which was also concealed up to now.]

"Introduction to metaphysics" accordingly means: leading into the asking of the fundamental question.

Pp. 19...21

And MH goes on to lecture about his question, and leaves aside the why, prima causa, question of metaphysics from Plato to Nietzsche.   ¶ 8:57 AM