Likutei Halachot: Ad d’lo Yada I
A person is obligated to drink on Purim until he no longer knows the difference between “cursed Haman” and “blessed Mordechai.” (Megilla 7b)
This is the aspect of “A person is obligated to drink on Purim until he no longer knows the difference between ‘cursed Haman’ and ‘blessed Mordekhai” (Megilla 7b). For Purim is the primary [time] for subjugating the filth of the serpent, which is sadness, the aspect of “in sorrow shall you eat of it” (Bereishit 3:17), as stated above. At that time, we must raise the joy from the depths of the kelipot… until we merit by way of the joy to achieve the aspect of the nine palaces as stated above, through which we attain the infinite light … which is the aspect of the goal of knowledge that we are not to know, as stated above. Therefore, a person is obligated to drink, that is, to get drunk on Purim for the sake of the joy, as it is written: “Wine that gladdens the heart of man” (Tehilim 104:15).
And he must increase the joy until he merits by way of the drunkenness and the joy of Purim to reach the aspect of the goal of knowledge that we are not to know, which is the aspect of “until he no longer knows, etc.” For the primary hold of good and evil, which is the aspect of “blessed Mordekhai” and “cursed Haman,” is from the tree of knowledge of good and evil, the root of which stems from “nirgan mafrid aluf” (“a whisperer separates close friends;” Mishlei 16:18). That is, it separates the aspect of Keter, which is the aspect of alef, the aspect of wonder which orders and settles the minds, thereby preventing the minds from their pursuit.
For the primary attainment of knowledge is precisely the aspect of the goal of knowing that we are not to know. For the aspect of not knowing is the primary goal of knowledge. For he who merits this, knowledge and lack of knowledge are contained together, they being the aspect of pursuit and hindrance, which are truly one at their root. Then evil is altogether nullified, for the primary hold of evil is the lack of knowledge and its concealment, which follows from the excessive light that causes the vessels to shatter.
This is because they do not contain knowledge and lack of knowledge together (as will be further explained below with God’s help).
Therefore, on Purim we must get drunk to the point that we reach such joy until we merit the aspect of the aforementioned goal of knowledge, where pursuit and hindrance are combined, they being knowledge and lack of knowledge. The two are combined together in the aspect of the goal of knowledge that we are not to know, where all evil is entirely nullified, as explained above.
This is the aspect of “until he no longer knows the difference between ‘cursed Haman’ and ‘blessed Mordekhai.'” For there we cannot talk about good and evil, for there all is one, all is good, as mentioned above. (Likutei Halakhot, Hilkhot Nefilat Apayim 4:7)