The issue of the Achoraim (posterior) concerns primarily the absence of Light of Wisdom, which is the essence of the vitality, called “Direct Light.” And this Light was restricted so as to not come to disparity of form. This is why ZON have no Gar when they are not corrected, so the Sitra Achra would not draw.
Yet, since there is a lack of Gar, there is fear that the external ones will have a grip. This is because they enjoy wherever there is a deficiency in the Kedusha (Sanctity), since they come and ask the “where” question, and it is unrealistic to answer this question before there is Hochma (wisdom). Hence, there is a correction to ZON: they rise and become integrated in Bina, considered, “for he delights in mercy,” and rejects Hochma, while Bina herself has no need for Hochma, since she herself is essentially Hochma.
This is called following their Rav’s view in everything, that their whole foundation is their root, meaning their Rav’s view. And the question, “Where is His honor?” is irrelevant there.
And they are in Bina until they are corrected by raising MAN of efforts and labors, until they are purified from reception for themselves. Then they are qualified to receive Hochma, and only then are they permitted to disclose their own discernment, as they are deficient, since they do not have Hochma, and to accept the answer, to extend the Light of Hochma to shine in them by way of illumination of Hochma. In that state they are in their own authority, and not in the authority of Bina. This is because they have the Light of Wisdom, and Light clears and expels the external ones. And perhaps this is the meaning of, “Know what to answer an Epicurean.”
This is called “one wall,” meaning the Achoraim of Bina, which is enough for both, and which is a shield from the Sitra Achra. In other words, by relying oneself on the view of one’s Rav, by being one with one’s Rav, it means that the wall that his Rav has, being “delighting in mercy,” is sufficient for him, too. However, afterwards they are separated, when he extends illumination of Hochma and can be on his own by being able to answer all of the Sitra Achra’s questions.