At long last, harrisimo02, thanks to the kindness of an old friend (Prof. Edwin Floyd at the University of Pittsburg), we're able to give you the text of "Aristotle" that you requested.
Introducing his 30th "problem," the author raises the question, Διὰ τί πάντες ὅσοι περιττοὶ γεγόνασιν ἄνδρες ἢ κατὰ φιλοσοφίαν ἢ πολιτικὴν ἢ ποίησιν ἢ τέχνας φαίνονται μελαγχολικοὶ ὄντες
"Why it is that all who have turned out to be outstanding men of science or politics or literature or the arts are apparently of melancholic temperament."
[In those days, "melancholic" (literally, "black-biled") meant pretty much what we mean by "depressive" or "manic-depressive" today.]
Boiling the sentence down to its core, we have the statement that Seneca focused on, and that you wanted to discover: All who have turned out to be outstanding men are apparently of melancholic temperament which, in Greek, is
πάντες ὅσοι περιττοὶ γεγόνασιν ἄνδρες φαίνονται μελαγχολικοὶ ὄντες, or, in caps,
ΠΑΝΤΕΣ ΟΣΟΙ ΠΕΡΙΤΤΟΙ ΓΕΓΟΝΑΣΙΝ ΑΝΔΡΕΣ ΦΑΙΝΟΝΤΑΙ ΜΕΛΑΓΧΟΛΙΚΟΙ ΟΝΤΕΣ