After the nature stuff.
I just finished my first "deep" read-through of Aristotle's Metaphysics. I used the Loeb edition, followed along in the Greek, made numerous marginalia, etc. I guess that I hadn't realized just how much space he devotes to the existence of numbers. All in all, three things come to mind:
(1) Avicenna once said that he read the Metaphysics forty times before understanding it. Well, if he meant complete comprehension, I can sympathize.
(2) The next time I read the Metaphysics, I will bring Averroes and St. Thomas along . . . for a longer ride.
3) Meditating on this stretch of Aristotle drives home to me my inadequate familiarity with the later Plato, especially the lesser dialogues, and with Plotinus.