Summation of question: Why does R. Meir say they are not believed to say that they were forced to sign?

Answer #1 (Rav Chisda): He holds that witnesses should forfeit their lives rather than sign falsely.

Objection (Rava): If they would consult with us, we would instruct them to sign and live. Why shouldn't we believe them?!

One may transgress anything to save a life, except for idolatry, incest, or murder.

Answer #2 (Rava): (The case is, the borrower admits that the document was valid, but he says that he paid.) R. Meir holds like Rav Huna:

(Rav Huna): If Shimon agrees that a document (that says that he owes Reuven) was written properly, Reuven need not prove that the signatures are valid. (We do not say that Shimon is believed Migo (since) he could claim that the document was forged.)

Rav Nachman (to Rav Huna): You deceive people! If you hold like R. Meir, say that the Halachah follows R. Meir! (By saying the law in your own name, you imply that all agree to it!)

Rav Huna: How do you hold?

Rav Nachman: In such a case, I tell Reuven to verify the signatures first. (If not, we believe Shimon due to the Migo.)

(Rav Yehudah): If he says that the document is Amanah (the borrower trusted the prospective lender and gave to him the document before the loan was given), he is not believed.

Question: Who claims that it is Amanah?

Certainly, the borrower is not believed to say this!

If the lender says this, he should be blessed for his honesty (we need not teach that he is believed)!

Answer #1: We must say that the witnesses are saying this.

Question: If we can verify their signatures without them, of course they are not believed! If we cannot verify their signatures without them, why shouldn't they be believed?!

Answer #2 (Rava): Really, the borrower claims that it is Amanah. He is not believed for the reason of Rav Huna (since he admitted that the document was written properly, he is not believed with a Migo that he could have said that it was forged).

Answer #3 (Abaye): Really, the lender says that it is Amanah. It is a case where his admission hurts others (his creditors), like R. Nasan's law:

(R. Nasan): If Reuven owes to Shimon and Shimon owes to Levi, we take money from Reuven to pay Levi - "He will give to the one to whom the principal is due".

Answer #4 (Rav Ashi): Really, the witnesses say that it is Amanah, and we cannot verify their signatures without them. They are not believed, due to Rav Kahana's law:

(Rav Kahana): One may not keep a document of Amanah in his house - "Do not let Avlah (fraud) dwell in your home".

(Rav Sheshes brei d'Rav Idi): From Rav Kahana's law we learn that witnesses are not believed to say that the document they signed was Amanah.

This is because witnesses do not sign on Avlah.

(R. Yehoshua ben Levi): One may not keep in his house a document for a loan that was paid - "Do not let Avlah dwell in your home".

(Rav): "If there is sin in your hand, distance it" refers to a document of Amanah or Pasim (a document which was written only to make the alleged lender appear rich). "Do not let Avlah dwell in your home" refers to a paid document.

R. Yehoshua forbids keeping a paid document, all the more so he forbids keeping a document of Amanah;

Rav Kahana forbids keeping a document of Amanah. He permits keeping a paid document. Sometimes the lender keeps it until the borrower pays the cost of the document.

(R. Ami): One may keep an uncorrected Sefer (of Tanach) for 30 days, but no longer - "Do not let Avlah dwell in your home."

(Rav Nachman): If witnesses say that the document they signed was Amanah, or that there was a Moda'ah (the seller told the witnesses that he was being coerced and intends to nullify the sale when the coercion ends), they are not believed.

(Mar bar Rav Ashi): If witnesses say that the document they signed was Amanah, they are not believed. If they say there was a Moda'ah, they are believed.

Amanah should not have been written, but a document for which there is a Moda'ah may be written.

Question (Rava of Rav Nachman): If witnesses say that what they signed was subject to a condition (not written in the document), are they believed?

You (Rav Nachman) say that they are not believed to say that the document was Amanah or that there was a Moda'ah. If this is because this uproots the document, the same applies to saying that it was conditional!

Or, perhaps a condition is a separate matter (it is not considered uprooting the document)!

Answer (Rav Nachman): When such cases arise, I tell (the buyer) to fulfill the condition (i.e. the witnesses are believed to say that there was a condition).

(Rav Papa): If one witness says that it was on condition and the other says that it was not, both agree that the document is valid. We now have one witness saying that there was a condition. One witness is not believed against two (the signatures, which imply that the document is unconditional.)

Objection (Rav Huna brei d'Rav Yehoshua): If so, this should apply even when both witnesses say that there was a condition (they should not be believed to change their testimony)!

(Rav Huna brei d'Rav Yehoshua): Rather, when both say so, they uproot their testimony. Also when one says that it was conditional, he uproots his testimony (and we are left with only one witness on the document, which is insufficient).

The Halachah follows Rav Huna brei d'Rav Yehoshua.

(Beraisa): If David and Levi signed a document and died, and two witnesses recognize the signatures but say that David and Levi were coerced, children or invalid witnesses at the time, they are believed;

If two other witnesses recognize the signatures, or if David and Levi signed other documents that were validated by Beis Din after there was a dispute over them, we do not believe the ones who disqualify the document.

Inference: It is valid, and the lender may collect with it.

Question: Why do we rely on David and Levi more than on the ones who say that they were coerced, children or invalid witnesses at the time?