Suppose a boy was born Bein Hashemashos. Since this is a period of "maybe it's still day, maybe it's already night," seemingly the doubt would translate into "maybe he was born on day 1, maybe he was born on day 2."

Consider 13 years later. Since we're stringent regarding Biblical doubts, this boy would seemingly have to act on day 1 as if he is already a Bar Mitzvah, yet simultaneously would not be able to fulfill others' obligations on the presumption that he is not yet a Bar Mitzvah. By day 2 he's a Bar Mitzvah either way and the doubt is settled.

On Bein Hashemashos on the evening of this boy's Bar Mitzvah, between days 1 and 2, would he be able to fulfill others' obligations by a sfek sfeka?

By the same definition of Bein Hashemashos being "maybe it's still day, maybe it's already night," one can pose that "maybe day 1 is his Bar Mitzvah, and even if day 2 is his Bar Mitzvah, maybe it's already night and therefore day 2." The doubt is also reversible: "maybe it's already night and therefore day 2, and even if it's still day 1, maybe day 1 is his Bar Mitzvah anyway."

Or perhaps since both doubts ultimately stem from the same question of whether Bein Hashemashos is day or night, it would be considered one doubt and not two?

  • Is this a sfek sfeka as much as a mima-nafshach?
    – Double AA
    Jun 16, 2020 at 17:51
  • @DoubleAA How is that mima-nafshach ? Jun 16, 2020 at 17:53
  • 1
    @AlaychemRememberMonica Whether time X is night or day, it's still been 13 years since time X 13 years ago.
    – Double AA
    Jun 16, 2020 at 17:57
  • To elaborate on DoubleAA’s point, if it’s already the next day then his birthday is the next day. If it’s still the previous day then his birthday was the previous day. (Unless you’re asking about two different points within bein hashemashos, where it’s actually possible that one point is the previous day and one point is the next day.)
    – Alex
    Jun 16, 2020 at 23:46

1 Answer 1


Here are three possible reasons why this might not work:

  1. This Sfek Sfeka would tell us that he was born earlier, that would be against the chazoko that his mother was pregnant.

  2. The two sefekus do not start at the same time, one starts when he is born or day one, and the second safek by bein hashemashos.

  3. Whatever you would want him to do, might be a davar sh'yesh lo matirim, since he can do it later. [Y"d shach 110/56]

  • For the third point, in re: davar sh'yesh lo matirin, isn't that always true? Whatever I want a gadol to do in bein hashmashot, he could do later when it is definitely night. Jun 16, 2020 at 22:41
  • Third point might not be true for, ex, leading the Tzibbur as Chazzan and saying Barchu and Kaddish during Maariv.
    – DonielF
    Jun 16, 2020 at 23:54
  • @DonielF Aren't those cases D'Rabonon and one safek would be enough ? Also one can be misplalel later, which might make it a "yesh lo matirin". Jun 17, 2020 at 0:37
  • @Ze'evmissesMonica Can you please give me an example. Jun 17, 2020 at 0:39
  • How can you say kiddush in bein hashmashot as you can definitely do it later? Or count sefira? Or say Maariv? There are likely better examples. Jun 17, 2020 at 2:04

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