We ended off the discussion of Shabbos when lost in the desert with a question on the Rambam. The Rambam states (Ma'achalos Assuros 14:13) that there is no issur of ma'achalos assuros for someone lost in the desert. 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. However, the gemara (and the Rambam) allow for work on Shabbos to be done by someone lost in the desert only for the sake of pikuach nefesh and only as necessary. What is the difference between these two cases?
The Rogatchover explains that Rambam reflects a fundemental difference between time and other objects (and this brings us back to the distinction in the previous post between bitul of objects and bitul in time.) Being lost in the desert allows for a suspension of the laws of ma'achalos assuros so that a person can travel as fast as possible. Foods which would otherwise be prohibited are now classified as permissable -- the situation has transformed the cheftza into a different object from its original state. In other words, that piece of chazir is not trief food that you are allowed to eat because of dire straits, but rather the chazir is no longer treif! Therefore, there is no need to eat less than a k'zayis or avoid eating in until on the verge of death.
The same reasoning cannot be applied to Shabbos. Food is an object present in its totality and can be transformed from issur to heter, but time does not exist yet until each second happens. Time is not a cheftza which we can make permissable. All we can do is make an allowance for the person, the gavra, to perform work as each second occurs. In doing so, we must view each second individually (which brings us back to the point in post 1 and post 2 of this series) and rely on the need of the individual to cause the dispensation to occur.