Our Sages defined a chacham as one who is roeh et hanolad, who foresees the results of his actions. We live in a world which is focused on the here and now, with only the great amongst us able or even willing to try and see the impact on tomorrow of what we do today. “Ulla said: Three things the end was allowed due to the beginning, and these are they; placing leather hides before those who trample upon them, returning shutters, and replacing a bandage in the Temple” (Beitzah 11b).
Until the advent of modern refrigeration, in order to have fresh meat for Yom Tov, one would slaughter an animal on Yom Tov itself. However, one could not prepare the skins of the animal for use as leather, as such went beyond food preparation on Yom Tov. However, not wanting to risk the loss of the hides, many decided not to slaughter the animal in the first place, depriving themselves of the joy of the festival. The Sages thus allowed one to place the hides in a public place where many would trample on them, preserving them for future use, so that there would be no hesitation to slaughter the animal.
The second “ending” allowed by the rabbis was the putting back of shutters on food stalls so that people would not hesitate to remove the cover to get food. This should have been forbidden, as may run afoul of the prohibition of building. The third case was “replacing a bandage in the Temple”. The kohanim performing their Temple service were not allowed a chatziza, a barrier, to come between their bare hands and any animal or vessels that they might handle. While normally, one may not replace a bandage on Shabbat, had the Sages not allowed such, kohanim would be hesitant to remove the bandage in the first place, and thus be disqualified from working in the Temple.
What I find most interesting is a “fourth case” brought in the name of Rav Yehuda that “even one who opens his barrel [of wine] or begins his dough on the holiday, Rav Yehuda says he may finish”. What helped make the shalosh regalim so special was how Jews from all walks of life would come together in Jerusalem to celebrate with their families, the community joining together in national joy. During Temple times there were those known as chaver(im), who were meticulous regarding the laws of tumah and tahara, purity and impurity, at all times. They were careful not to eat food handled by an am haaretz, one who did not adopt such a practice and whose food was not carefully guarded to ensure purity. There was no such requirement to be careful about impurity unless one was planning to go the Temple or eat sacrificial food, something all would do during the Yamim Tovim. While there was no way to ensure that the amei haaretz would properly observe the laws of purity on the Yamim Tovim, Jewish law trusted them to do so and treated all who came to the Temple on Yom Tov as being in a state of purity. While this was surely not universally true, we did not want to embarrass anyone—especially those coming to the Temple to celebrate Yom Tov—and declare that which they came in contact with to be impure. Given a choice between strict standards of “purity” and possibly embarrassing someone, Jewish law chose to be careful about the latter.
What Rav Yehuda and the Sages debated was the status of food handled by an am haaretz after Yom Tov. The Sages were of the view that the leniency with regard to purity applied only on Yom Tov itself. With Yom Tov over and people dispersed to their homes, the same food that was considered pure on Yom Tov was retroactively considered tameh. Merchants who had provided food for the masses of Jews arriving in Jerusalem for the holidays had to be careful not to sell such food to a chaver once Yom Tov was over.
While this retroactive change in status may seem strange—either the food is tameh or not, and a change in date should have no impact—all legal systems balance many factors before arriving at a ruling. The ability of all Jews to join together and the extreme care we must exercise so as not to embarrass anyone resolved the doubt regarding the food towards leniency. These factors did not apply after Yom Tov and hence, the doubt had to be resolved in a stringent manner. Rav Yehuda agrees in theory, but not in practice, “allowing the end because of the beginning”. If we did not allow merchants to continue selling their produce after Yom Tov, they might not sell it during the holiday either, fearing much left over and few potential buyers. Those travelling to Jerusalem for Yom Tov would then not have readily available provisions.
Once again, we see how a single Jewish law takes into account not only the case before us, but the impact any decision rendered would have. Legal theory and legal practice must, if need be, part ways.
 On the heels of the seder, it is worth noting that this is one of the distinguishing features between the question of the chacham and that of the rasha. The question of the rasha is introduced with the phrase, “and when your children shall ask you”, while that of the chacham begins, “and when your child will ask you, machar, tomorrow”. Thinking beyond today makes all the difference.
 It is similar reasoning that allows a doctor called into emergency service on Shabbat to travel home on Shabbat once he has administered the necessary medical care. Whether one may drive his own car or instead have a non-Jew drive him home is dependent on whether “allowing the beginning because of the end” is rooted in biblical law or is a rabbinic innovation. If it is the latter, and most authorities assume such, this principle may only be invoked to violate rabbinic law.
 While in modern parlance, an am haaretz refers to one who is ignorant in the Talmud, the term is most often used to describe those who were not careful about the laws of purity.
 This is no different than convicting someone on civil charges, yet finding them innocent for the same “crime” in a criminal trial. The rules of evidence are, as they should be, different when dealing with money, as opposed to life-and-death questions