Modim, modim (woops, can't say that)
Modim anachnu lach. Archetypal Prayer of Thanksgiving (our prayers are usually broken down into Praise, Request, and Thanksgiving). Except that when there's a minyan, we say an alternate version during the repetition, the Modim Derabbanan. And there, folks, is a mystery.
R' Alan Brill, in last week's Philosphy of Prayer class at Drisha, noted that the prayer in the Amidah is what he calls "entreaty", rather than "petitionary" prayer. Petitionary prayer is asking for X in return for Y. E.g., a misheberach - please bless so-and-so because I'm pledging to tzedakah, or because the congregation is praying on their behalf. But when we look at the intermediate brachot (4-16 in the daily prayers), where we ask for stuff, we ask in the merit of God's goodness - because You are a great healer, heal us; because You are great in forgiveness, forgive us. R' Mayer Twersky, following (I think) his grandfather RYB Soloveitchik, explains those blessings as expressions of confidence that God will do X or Y, not actual requests that He do X or Y (leaving out the insertions for health and prosperity).
However, Modim Derabbanan, the additional Modim, which is a collection of alternate Modims offered by different rabbis in the Talmud (Sotah 40a), all versions clearly end "al she'anu modim lach", "because we thank You". We thank You ... for giving us life, ... so You shall continue to sustain us, and return us from exile so that we may fulfill Your laws completely, because we thank You" And that's clearly a request. We expect that You will do X and Y, because we thank You. Our thanking Him creates the quid-pro-quo of petitionary prayer.
Rashi tries to avoid the issue, by reading it as a repetition of the first phrase, making it "thus You shall do X and Y ... because You inspired us to cleave to You and to thank You". Which makes little enough sense, although perhaps, it can be read as "You do X and Y to create an environment where we are obligated to thank You", but since they are future needs, such as redemption, that explanation doesn't make much sense to me.
Artscroll takes Rashi one step further. They write
"[We thank You] for inspiring us to thank You."
Not only does it turn the phrase around, and insert "inspiring us" (following Rashi), it then adds the bracketed passage "[we thank You]" which makes the whole thing completely incoherent, and unrelated to the Hebrew.
The Hebrew is simple enough, despite Rashi's attempt to revise the words of Chazal: it's a petitionary prayer. If Chazal put it in, it must be OK, even if it's not OK enough for Rashi or Artscroll. Even the Beis Yosef (R' Yosef Caro) understands this literally, contra Rashi. He gives both Rashi's emendation and the clear simple meaning.
"because we thank You" into "we thank You for inspiring us to thank You". Incoherent babble in the name of revisionism. I thought it was only the heterodox prayerbook authors who took such liberties with their translations. Apparently I was wrong.
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Just for reference, here's the relevant passage in the Soncino translation:
While the Precentor recites the paragraph 'We give thanks' what does the congregation say? — Rab declared: 'We give thanks unto Thee, O Lord our God, because we are able to give Thee thanks'. Samuel declared: 'God of all flesh, seeing that we give Thee thanks'. R. Simai declared: 'Our Creator and Creator of all things in the beginning, seeing that we give Thee thanks.' The men of Nehardea declared in the name of R. Simai: 'Blessings and thanksgiving to Thy great Name because Thou hast kept us alive and preserved us, seeing that we give Thee thanks'. R. Aha b. Jacob used to conclude thus: 'So mayest Thou continue to keep us alive and be gracious to us; and gather us together and assemble our exiles to Thy holy courts to observe Thy statutes and to do Thy will with a perfect heart, seeing that we give Thee thanks'. R. Papa said: Consequently let us recite them all.
We follow R' Papa - we say them all. Rashi explains that each came and added their phrase onto the previous ones.
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And, looking around the Web, I see this was already discussed on mail-jewish 12 years ago. Oh well, אין חדש תחת השמש.