On Purim we are bidden to get so thoroughly drunk on wine or other intoxicants that we are unable to distinguish between good and evil:
Rava said: one is obligated to become inebriated on Purim until he does not know (ad delo yada) the difference between “Cursed is Haman” and “Blessed is Mordechai”. Talmud Bavli, Megillah 7b.
While halakhists dispute the question of whether this is meant literally and whether it is halakhically required or even advisable, See David Golinkin, “To Drink or not to Drink” , the notion of drinking oneself into oblivion on Purim is certainly part of the Jewish tradition, and is widely observed. The Lubavitcher Rebbe explains this unusual religious rite as follows:
Nothing created by G-d has a negative purpose… On Purim we are required to elevate our understanding to the point that we perceive no essential distinction between Mordechai and Haman. For the ultimate goal in the creation of Haman is that he become a force for good, like Mordechai… Self-transcendence is the goal of our drinking on Purim. The state which transcends the limits of reason is related to the concept of transforming evil to good. From an intellectual perspective, good and evil have clearly defined boundaries… However, the infinity of G-d’s essence (and likewise, the infinite potential of our souls) is not bounded by these limitations. At this level, “darkness is like light” (Psalm 139:12). Summary of Likutei Sichos 7, Vayikra 3 inhttp://livingjewish.net/chassidus-page/a-mitzvah-to-drink.
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