This text-based class on Likkutei Sichos vol. 21 Parsjas Bo explores the debate in the Mishnah between Rabbi Shimon and the Rabbis if relatives are accepted as witnesses that they saw the new moon, in order to establish Rosh Chodesh.

The class explores the question why do we, in Jewish law, believe two witnesses? Is it statistical truth or Halachik truth? And why is it that by this particular law, we don't rely only on two witnesses, as with all other Torah laws, but we require astronomical calculations to go along with the testimony? As it turns out, this represents two fundamental approaches to all of Judaism.