Rashi quotes the case in Kiddushin 63a, where a man says to a woman, "I'm married to you on condition that I convert" (which R'Meir says works) and makes the comparison to the case of peiros dekel in Bava Metzia 66b, where Rav Huna says it's a good sale.
In the case of Kiddushin, presumably, the convert is the davar she lo ba l'olam. To translate that to peiros dekel terms, he is the peiros, i.e. he's the davar hanikneh that doesn't exist at shaas mecher.
But isn't the mechanics of Kiddushin that it's the woman who's the davar hanikneh, she is makneh herself to the baal and then becomes nikneh to him? In the example Rashi quotes, she is Jewish and very much b'olam at shaas Kiddushin!
Maybe Rashi was just quoting the case where the man was the convert, even though it's not directly parallel to peiros dekel, as an introduction to the sugya of davar she ba l'olam, where the Gemara in Kiddushin lists a number of cases that work according to R'Meir, including...
Where the woman says to the man,"I'm married to you on condition that I convert", where she's the davar hanikneh, and as still a non-Jew, she's not yet b'olam at the time of the sale.
But still - what transaction takes place at the beginning between the makneh and the koneh, when either he (according to the case Rashi quotes) or she (which seems like a more parallel to peiros dekel) had not yet converted, even if the Kiddushin occurs retroactively? At that time either the koneh - according to the case Rashi quotes - or the makneh - where she's the convert - was not yet Jewish?
Daniel Steinberg, Columbus, OH USA
Dear Daniel,
First of all, Rebbi Meir holds that the transaction of Lo Ba l'Olam works and takes effect only when possible, after he converts and not retroactively at all.
The Gemara in Gitin 13b, discussing the view of Rebbi Meir, mentions both Lo Ba l'Olam of the object and also of the purchaser. Rav Ashi there says that Rebbi Meir says "Makneh" by the object but there is no Kinyan if the purchaser is Lo Ba l'Olam, like a not-yet-born child. But still, Rebbi Meir does validate the Kidushin of a future Ger! Tosfos in Kesuvos (58b, DH l'Achor) explains that since he exists in the world at least as a Nochri, he is more in the world than the unborn child, and it is parallel to the case of Lo Ba l'Olam of an object which, according to Rebbi Meir, works.
All the best,
Reuven Weiner