Rava says ein ones b'gittin. this i understand to mean that the get is valid as a get despite the oness. rava is saying that in the absence of any evidence of a d'oraisa positon one way or the other, the rabbanan, in the interest of judicial certainty (tznuos u'prutzos) will rule the get valid at the time the t'nai expires.
kol mekadesh al d'aatah d'rabbanan mekadesh means the parties accept this position and afkinon rabbanan l'kidushei minei refers to now, not retroactively. what does b'eilas znus have to do with anything? no one is changing the status l'mafreia?
David Willig, Perth Amboy NJ, USA
As I understand it, you are asking why the Gemara assumes that the only way for the Rabanan to remove Kidushin is retroactive. Why can "Kol d'Mekadesh" not be applied to remove it from here on? An exellent question.
I see only two ways for "Kol d'Mekadesh..." to possibly remove Kidushin from here on (and not retroactively):
(1) By having every person make their Kidushin, from the start, in such a way that it should "expire" as soon as the Rabbanan want it to.
I don't think this can be done. Kidushin doesn't just expire; it needs a Get to end it (Nedarim 29a).
(2) The other, more serious, suggestion is that just as Kidushin is enacted according to the wishes of the Rabanan, so too Gerushin. (This is not only logically sound, it is actually the truth, according to Teshuvos Rashba cited by the Gilyon ha'Shas and a few other Rishonim.) If so, when a person gives a Get, let us assume he wants it to take effect as the Rabanan wish. Therefore, even if the Get does not work mid'Oraisa (because the Tenai was fulfilled b'Ones), the Rabanan can make it work, and end the Kidushin from here on through "Kol d'Megaresh..." Why doesn't the Gemara accept this possibility?
The answer is that the Gemara never applies Kol d'Mekadesh (or d'Megaresh) to effect a Kinyan. The clause only allows the Rabanan to annul a Kidushin or Gerushin that was made. They cannot effect Gerushin with that principle, they can only retroactively annul the Kidushin through that application of that principle in order to release the wife from her husband. (Kol d'Mekadesh is just a clause in a Kinyan, not a Kinyan in its own right.)
Be well,
Mordecai Kornfeld