There are various reasons that the Poskim nowadays give to explain that there still is a concept of Nidda Min Hatorah despite women not having a Hargasha. From what I have managed to see, there seem to be three approaches:
- The Aruch Hashulchan writes that a woman has Hargosho but doesn't recognise it.
- An approach based on the Sidrei Tahara that Hargasha is an indicator that the dam came from the mekor.
- Tumas Nidda was based on what is normal: Then, it was Hargasha; now, it is Derech Reiya.
I have found all these approaches very hard to understand. It would seem that when a woman does a Bedika, we are suddenly concerned that she may have had a Hargosha. If so, why do Kesamim not create such a concern for hargasha, as there is no minimum limit for Dam with Hargasha (possibly one needs a minimum of two drops - Bach 183)?
Could it be that Nidda nowadays is only Miderabnan? This would seem to be the simplest approach but no one seems to want to go with this approach.
Or one could learn the other way based on the Aruch Hashulchan and make the novel suggestion that nowadays there is no Hilchos Kesomim as we say that we are always concerned that a woman had a Hargasha but she didn't feel it just as we say when a woman does a Bedika that it is a Sfeika De'oirayso? R' Moshe explains the Aruch HaShulchan that this was only said by a woman getting her regular period but we are not concerned in that way in the case of a Kesem. So the question I had on it is: Why are we concerned that a woman had a Hargasha when she does a Bedika then?
Is there another approach to explain this?