אי אפשר בפתיחת הקבר בלא דם

Today’s daf (Nidda 21) has a machlokes Rav Yehuda and Rabanan whether אפשר בפתיחת הקבר בלא דם or not. There is a machlokes the Rambam and the Rosh how to pasken and this question is very relevant הלכה למעשה when doing various medical procedures.

The question we need to ask is, isn’t this a machlokes in מציאות? It should be a biological fact. So why not just check it out. The standard answer given is that everyone agrees on the facts that there is a small percentage of time that blood comes out. The machlokes is whether that percentage is significant enough to make a rule or not.

I find that hard to believe. The Gemara gives no hint of that and certainly sounds like it’s a machlokes in מציאות.