Bava Metzia page 28b

I got to the sea, and then on the way back, it suddenly occurred to me how to answer a question in the Rambam in a way that is close to what Rav Shach says. [Laws of robbery and Lost Objects 13:17] The idea that occurred to me is this. When a person is guarding a lost object, he is a paid guard. But if the object will lose all its value if it is kept around too long a time, the guard must sell it, and guard the price of the sale. Therefore, he is a borrower, not a paid guard. There should be no ambiguity about this since guarding a lost object is not the same as guarding the money someone paid for it. While often we say what is worth money is money, still that is not universal, and we usually require a special verse to show us this. [See the beginning of Kidushin, and the sugia of paying double for theft where this is an argument.] And the fact that The Rambam holds the guard becomes a borrower is no problem in itself. After all, he is just quoting R Yose in Bava Metzia page 28b] who says if the money of the sale is lost with a by an unavoidable accident, he must pay for it like the law of a borrower, not a paid guard. The only question is why is he not a borrower of money instead of a borrower of an object? And the answer I think is this. The lender did not lend him anything. Rather he lost an object, and the sages instituted this law of selling the object, and being allowed to use the money. That is a borrower of an object, not a borrower of money. How can you be a borrower, if there is no lender? Besides that, the statement the value of money is like money means an object can be used instead (in place of) of money, not the money can be used instead of the object. I said this idea to Rav Brodi (a rosh kollel in Netanya) and he asked, “What would be the law if there was no permission to use the money of the lost object?” His point is that he still has an obligation to guard the money as if it was the lost object itself. I countered this argument by mentioning that that would be the opinion of R Akiva who disagrees with R Jose, and holds the finder cannot use the money. So, it would be the opinion of R Jose that he can use the money, and he becomes a borrower right away even before he uses the money. However, I realize that this objection of Rav Brodi might be the reason that Rav Shach found a different answer for the Rambam. However, Rav Shach answers that he is liable because the Torah places a obligation on him to guard the lost object and so there is a higher degree of responsibility by the permission to use the money that is it was a case of a deposit. -------------------------------At any rate, I got to the sea, and then on the way back, it suddenly occurred to me how to answer a question in the רמב''ם in a way that is close to what רב שך says. [ה' גזלה ואבדה י''ג:י''ז] The idea that occurred to me is this. When a person is guarding a lost object, he is a paid guard. But if the object will lose all its value if it is kept around too long a time, the guard must sell it, and guard the price of the sale ויכול להשתמש בכסף. Therefore, he is a שאול, not a paid guard. There should be no ambiguity about this since guarding a lost object is not the same as guarding the money someone paid for it. While often we say what is שווה כסף ככסף, still that is not universal, and we require a special verse to show us this לפי זכרוני . [See the beginning of קידושין , and the סוגיא of paying double for גנבה where this is an argument.] And the fact that The רמב''ם holds the guard becomes a שאול is no problem in itself. After all, he is just quoting ר' יוסי in בבא מציעא כ''ח ע''ב] who says if the money of the sale is lost by an unavoidable accident אונסים גדולים ,, he must pay for it like the law of a שואל, not a שומר שכר. The only question is why is he not a לווה of money instead of a שואל of an object? And the answer I think is this. The מלווה did not lend him anything. Rather, he lost an object, and the חכמים instituted this law of selling the object, and being allowed to use the money. That is a שואל of an object, not a לווה of money. How can you be a borrower, if there is no lender? מלבד זאת, שווה כסף ככסף פירושו שניתן להשתמש בחפץ במקום כסף, לא שניתן להשתמש בכסף במקום החפץ עצמו---------------------I said this idea to רב ברודי (a ראש כולל בנתניה) and he asked, “What would be the law if there was no permission to use the money of the lost object?” His point is that he still has an obligation to guard the money as if it was the lost object itself. I countered this argument by mentioning that that would be the opinion of ר' עקיבא who disagrees with ר' יוסי, and holds the finder cannot use the money. So, it would be the opinion of ר' יוסי that he can use the money, and he becomes a borrower right away even before he uses the money. However, I realize that this objection of רב ברודי might be the reason that רב שך found a different answer for the רמב''ם. ] רב שך answers that he is liable because the תורה places a obligation on him to guard the lost object, and so there is a higher degree of responsibility by the permission to use the money (than if it was a case of a deposit).