Eiruvin 37a, b

The rabbis continue their conversation regarding retroactive designation.  They are concerned that one might decide after Shabbat that an eiruv is valid/invalid.  They raise related issues, including the first and second tithes.  If one drinks wine, for example, and then retroactively designates tithes after they have finished drinking - leaving enough wine for terumah - is that retroactive designation valid? And what if the flask explodes before the tithing occurs? Additionally, the rabbis touch on leniency regarding rabbinic decrees and stringency regarding Torah law.  Looking at different individuals, the rabbis debate whether expectations should be different for chaverim than for amei ha'aretz.  Further, the rabbis argue about whether or not one must be consistent with these rules - either retroactive designation is valid in every case, or it is never acceptable.  Some rabbis push forward each of these ideas and others argue against their relevance.

The idea of retroactive designation opens up many potential issues.  Retroactive designation focuses us on the importance of intention.  Did we mean to do the right thing and we just forgot?  If that is the case, should we be able to "make good" after the fact?  Perhaps intention should not matter at all.  As long as we "make good", have we done enough?

I am always curious about the rabbi's reasons for arguing different positions.  I believe that they were well aware that they were not simply arguing about theoretical, philosophical ideas.  Rabbis were answering questions, mediating debates, acting as legal authorities, and mending relationships in their communities.  When they chose to argue one position over another in the mishna or gemara, it must have been informed by their experiences with real live human beings.  How did those interactions influence their logical reasoning?

I believe that knowing better the personalities of the different rabbis might be informative.  Eventually I hope to stretch my learning to include those details.  For now, I can only imagine and assume their motivations.