Both This and That? — Eruvin 91a
(1) תלמוד בבלי מסכת עירובין דף צא/א
רבי שמעון אומר אחד גגין וכו': אמר רב הלכה כרבי שמעון והוא שלא עירבו אבל עירבו לא דגזרינן דילמא אתי לאפוקי מאני דבתים לחצר ושמואל אמר בין עירבו בין שלא עירבו וכן אמר רבי יוחנן מי לחשך בין עירבו ובין שלא עירבו מתקיף לה רב חסדא לשמואל ולרבי יוחנן יאמרו שני כלים בחצר אחת זה מותר וזה אסור רבי שמעון לטעמיה דלא גזר
R' Chisda here expresses astonishment that both Shmuel and R' Yochanan should allow an inconsistency in Halachah that might lead to confusion: If you allow the transfer from yard to yard of both objects that originated in a house (that participated in the eruv of the one yard) and objects that originated from the yard itself (of a house that did not participate in an eruv), people will come to question: This one object may be transferred (from yard to yard), and this object may not be transferred?
A similar discussion appears in Gittin (18a), where Shmuel says that the three month period that a divorced woman must wait before remarrying begins from the date her get was written, not from the date that it was written. Here, R' Nosson bar Oshiya expresses astonishment: If you allow the remarriage to take place three months after the date on which the get was written, people will come to question: Two women divorced by the same man on the same day, one is permitted to remarry earlier and one later (depending on the dates of their gittin)?
Why does this question of consistency not seem to bother Shmuel specifically? Perhaps we can find a clue on the basis of the twin principles that halachah in monetary issues follows Shmuel and that halachah in monetary issues follows R' Nachman. We see in Bava Basra 143a that in a case in which one person says to another: "Acquire, you and the donkey together," R' Nachman rules — and the halachah hence is — that the person acquires half of the entity in question. But will not people come to question: The acquisition by the donkey is meaningless, yet the acquisition by the person is effective?
Evidently, dayanim like Shmuel and R' Nachman felt that Halachah must be precise, regardless of the impression that might be left in the process (see Gilyonei HaShas here and Teshuvos Yabi'a Omer, vol. 6, Even HaEzer 2:2).