We read in Parshas Vayera about the meritorious acts of the two daughters of Lot. They thought their entire region was destroyed, and that only they and their father had survived. They truly thought that they were saving the world! The Rabbis of the Talmud point out that because the older daughter stepped forward on the first night "to save the world", she was rewarded to a greater extent than the younger daughter (Bava Kama 38b).
When what the daughters had done became public knowledge, however, Avraham Avinu, their great uncle, was so embarrassed, he moved away from the neighborhood (Rashi 20:1). The daughters mistakenly thought that the entire area had been destroyed, including Avraham and his family, and that only they and their father were meritorious enough to have been spared, singled out by Hashem for the purpose of preserving humanity. For the sake of truly saving the world, even incest would be permitted (see Rashi to Vayikra 20:17).
In Shulchan Aruch (Orach Chaim 306:14) we permit one even to violate Shabbos in order to save someone else from shmad. This principle (that we encourage one to violate a lesser sin in order to save another individual from a much greater sin) only applies in very rare instances, where it is absolutely clear that the spiritual "investment" will certainly pay off in a most pronounced fashion. Every legal system contains a clause which says that in special circumstances we assume that "the end justifies the means". The various legal systems all differ from each other regarding the details of this principle, i.e. in defining acceptable ends.
In Halacha, pikuach nefesh is considered so important a goal, that in most instances it is justified to violate Torah laws when a conflict arises between a given law and pikuach nefesh.
At the start of the movement of chassidus, there were many Chassidim who would invest so much time "preparing" for the fulfillment of various mitzvos (such as tefilah, and the seder on Pesach night) [working with the assumption that the more one invests in "preparation" for a mitzvah, the more will be gained spiritually from the performance of the mitzvah] that they would not get to daven or to eat the matzah until after the appropriate time. They felt that this would be an acceptable example of "the ends justifying the means" ( chatei bishvil shetizkeh).
Rabbi Chaim of Volozhin, the student of the Gaon of Vilna, vigorously opposed this practice in his work "Nefesh Hachayim". When the mitzvah is performed after the zman, nothing is gained. One has not enhanced his spiritual gain from performing the mitzvah with so much extra preparation, but has rather lost all spiritual gain possible, since the mitzvah has not been fulfilled properly. One who recites shacharis after the correct zman is the same as one blowing shofar on Purim and reading the Megillah on Rosh Hashana. One who is off by half an hour is the same as one who is off by half a year. Rav Chaim concludes that the Talmudic principle that we sometimes recommend - chateih bishvil shetizkeh - only applied before mattan Torah! After mattan Torah all details of each Torah law must be adhered to without any exception.
Reb Osher Tiktiner, a student of Rav Chaim, points out in his sefer, "Keser Rosh", that this concluding statement is really an exaggeration. The Talmud and the Shulchan Aruch do speak of rare instances where we would recommend, even today, after mattan Torah, that one should sin in order to gain spirituality. But these are indeed very rare instances!
When one is forced with a situation of pikuach nefesh, even when in doubt, the concern for the pikuach nefesh takes precedence over the other Torah laws, even if the doubt is only a far fetched one. But regarding the daughters of Lot, the chumash points out that in truth, Lot and his daughters did not really merit to have been spared. It was only in the zechus (merit) of Avraham that G-d spared their lives (19:29).
Their assessment of the situation was totally in error. The Talmud points out that sometimes when there seems to be a medical emergency on Shabbos, and the laymen present have no way of determining accurately whether there is a concern of sakana (mortal danger), one must treat the case as one of safeik sakana. Even if later it is discovered that the chilul Shabbos was not at all called for. Nonetheless, since according to the perception of the layman there was a safek sakana, no kapparah will be needed for the chilul Shabbos (Menachos 64a). Quite the opposite - the layman deserves to be rewarded for taking care of what to him was a safeik sakana. So too in the case of Lot's daughters, although they were totally off in their perception, nonetheless they each deserved a reward for taking care of what they perceived as a major safeik sakana.
Rav Velvel Soloveitchik once commented that his father, Rav Chaim, was much greater than him; Rav Chaim, he explained, had such keen insight, that he had the ability to analyze a political situation so carefully such that he would be able to predict accurately what would follow in another sixty years if one route were to be followed, as opposed to the other route. Rav Velvel readily admitted that he did not at all have that ability. After pausing for a moment he added that he did, however, think that he possessed a certain degree of insight that others lacked - "at least I'm able to see what's under my nose!"
Many people engaged in kiruv have developed a distorted sense of reality. Many think that they're really saving the world. And, of course, in order to save the world they allow themselves certain leniencies and they take certain liberties, like the daughters of Lot, based on the principle of chatei bishvil shetizkeh! We ought all to take to heart the warning of Rav Yosef Dov Soloveitchik, once given to young musmachim, not to develop a messiah complex!