Continued from Part 1 and Part2: We left off last week discussing the halacha of someone lost in the desert who is allowed to work only as needed for pikuach nefesh and must designate one day a week as Shabbos with kiddush and havdalah. The MG"A asks why Shabbos must be observed on any day -- why not say that each day which is possibly Shabbos is bateil to the other six days that are definitely chol, eliminating the safeik. Josh M. commented last week that we cannot say bitul b'rov in this case because it is a case of kavua. In other words, if a city has 9 kosher butcher shops and 1 treif shop and a piece of meat is found on the street, the principle of rov tells us that the meat is kosher. But if I enter a store and remove the meat but am not sure which store I shopped out, the principle of rov does not apply. Because the stores are kavua, fixed entitites that I have intruded upon, the safeik is treated like a 50-50% chance and the meat may not be eaten. Days of the week cannot be pulled out of a hat; time is fixed in place and the person wandering the desert moves from one day to the next, making this similar to the din of kavua.
Although this answer is given by the MG"A, I would suggest another answer. Recall the Mishna Berura's question: why not violate Shabbos on one day to prepare enough food for the entire week and avoid work the other days, statistically minimizing the chance of chilul Shabbos. Last week I suggested that perhaps we do not view time as existing in units of weeks or months, but rather each moment must be viewed independently. One need not take into account future probabilities when determining the degree of chilul Shabbos permitted on any given day. This same reasoning will resolve the MG"A's question as well. The concept of rov applies when a drop of milk falls into a pot of meat, or the treif butcher store is mixed among a group of kosher shops. But time is not a mixture -- the future does not exist until it occurs and the past is gone already. Each moment is an independent unit! Whether or not you accept my answer to the M"B's question, at least with respect to the MG"A the idea that bitul does not apply to time is discussed in the Koveitz He'oros in Yevamos 27:5, so I have a friend for my sevara.
If you've been following this whole discussion, we now come to the icing on the cake. The Rambam writes (Ma'achalos Asuros 14:13) that there is no issur of ma'achalos asuros for someone lost in the desert who only has treif food to eat. Note that the Rambam does not refer to a starving person who is about to perish, but simply to someone lost -- the implication is that even a full k'zayis of treif food may be eaten by the lost traveller even before reaching the verge of death. Why is it that the Rambam and gemara make allowance to desecrate Shabbos only for the sake of preservation of life, yet the prohibition of eating treif food is suspended immediatly and apparently without any restriction once the person finds himself lost?