Early on in today’s daf (Ketubot 14a), reference is made to the position of Rabban Gamliel who – as I explained in my commentary to yesterday’s daf (https://rabbijohnnysolomon.com/ketubot-13) – rules that if a pregnant unmarried woman says that the man with whom she has had sexual relations does not render her ineligible to marry a Kohen, then she is believed.
On this basis, Rav Yosef then unconditionally applied the reasoning of Rabban Gamliel to a range of cases. However, Abaye then explained to him: הלכה כרבן גמליאל – ‘yes, the law is in accordance with Rabban Gamliel’, ואת לא תעביד עובדא עד דאיכא רוב כשרין אצלה – ‘but you should not rule in accordance [with Rabban Gamliel] unless in a situation where the majority of men living in her locale are fit for her (i.e. they would not render her ineligible to marry a Kohen)’. What this means is that while the law in theory is always in accordance with Rabban Gamliel, Abaye rules that the law in practice also depends on the variables of the situation.
As I explained in my commentary to Ketubot 10 (https://rabbijohnnysolomon.com/ketubot-10), there is a substantive difference between halacha in theory and in practice, and while there are halachot that are correct within the ‘four walls of the beit midrash’, they are generally not halachic policy – oftentimes for very good reason. This is because like pure – as opposed to applied – mathematics, they presume that the situation within which the law is being applied is totally frictionless and absolutely predictable, which is almost never the case in the real world.
Finally, it is often thought that halacha in theory is stricter than halacha in practice. However, as we see here in where Abaye applies the position of Rabban Gamliel, he is ‘stricter’ since he places limitations on the ruling. And why does he do so? Because while halacha in theory rarely needs to think about consequences, halacha in practice must always be cognizant of consequences.