Why does it say "Tachas ha'Shamesh"?
Metzudas David #1: It is under the sun's authority, i.e. gathering acquisitions, which depends on the Ma'arachah of Shamayim. He mentioned the sun, for it affects lower beings greatly, like it says above (3).
Metzudas David #2: It refers to this world, in which the sun shines.
How was he able to see everything Tachas ha'Shamesh?
Ri Kara: It is because he was king.
Metzudas David: Refer to 1:14:1:1.
Why is it all Hevel?
Seforno, Metzudas David: Everything Tachas ha'Shamesh, i.e. what perishes, its own purpose is inferior and unimportant.
What is "Re'us Ru'ach"?
Rashi: It is a broken desire 1 , like "Re'u Amim va'Chotu" (Yeshayah 8:9). The end of the deed leads to heartache. Rashbam - Ru'ach is desire, and Re'us is from the verb Ra'ah 2 , just like Demus is from Damah, Anus from Anah.
Ibn Ezra #1: This is like "Efrayim Ro'eh Ru'ach v'Rodef Kadim" (Hoshe'a 12:2) - it does not help or satiate 3 . Ru'ach is like Hevel. Due to his great deceit, one cannot seize him. This is like "Ki Ru'ach Yizra'u" (ibid. 8:7), "Ki Ru'ach Avrah Bo v'Einenu" (Tehilim 103:16).
Ibn Ezra #2: "Re'us" is thought - "Rayon Ru'ach" (17). The grammatical form of Re'us and Rayon is like Demus and Dimyon. The last letter of the root (Hei) is omitted sometimes.
Seforno: Everything that man rejoices over it is Re'us Ru'ach. He is fed from mere Ru'ach, like "Efrayim Ro'eh Ru'ach."
Metzudas David: This is because he does not attain his hope and desire. Metzudas Tziyon - Re'us is breakage, like "Tero'em b'Shevet Barzel" (Tehilim 2:9).
It seems that this is breaking. Rashbam explains how the words imply like Rashi says. (PF)
Rid: An event of nothing. The same applies to "Rayon Ru'ach" (17). He engages in folly. "Ro'eh Zonos" (Mishlei 29:3) engages in Zonos.
