Niddah 60: Three Women in the Same Bed: Public or Private?

We know that the rabbis decided that a woman should behave as if she is niddah even in situations where the Torah deems her ritually pure.  Today's daf ask a question about public verses private instances of finding kedamim, blood stains:  If three women slept in a single bed and blood was found under one of the them they are all ritually impure.  If one of them examined herself with a cloth and was found to be impure, she herself is deemed ritually impure while the other two are considered to be pure.  

The rabbis ask why any of the women should be considered to be ritually impure if the stain is under just one of them and they are permitted to be lenient.  They introduce a principal: safek tumah b'reshut harabbim, tahor: doubtful impurity in a public pace is considered to be ritually impure.  A public place is one with at least three people.  Because of this, the three women sleeping together are sleeping in a public place and questionable impurity should be treated with leniency.

Several answers are offered to address this question.  Here are three examples:

• three people might not constitute a reshut harabim, a public place.  If the three are in a hidden place, like these women in bed, it is considered to be a private place.
• the rule that doubtful impurity in the public domain is considered to be ritually pure only applies when the impurity comes from the outside, for example when someone stepped over a grave, but does not apply when that impurity comes from a person her/himself, like in the case of a ketem.
• If the women presented their cases separately they might have been deemed ritually pure.  When they all came together, one of them had to be the sources of the ketem and so they are all declared to be ritually impure.

Again, the rabbis are balancing their desire to allow women to be intimate with their husbands as frequently as possible with their felt need for providing structure and stringency.