Nefesh HaChayim, An Introduction by the Author's Son

Annotation: Perhaps this matter that is mentioned in Eruvin 13b: “...and if your eyes could see before you... ‘and your eyes will behold your teacher’” (Yeshayahu 30:20) is like the matter mentioned in the verse (Sh’mote 33: 23) “and you will see my back, but my face may not be seen”. It can be interpreted per Midrash Sh’mote, chapter 3 on “I will be what I will be”—My names reflect My actions (and all of the details of the final outcome were included in the initial conception in thought). For that reason the initial conception in thought is called “face”, for it precedes. And the action comes later. And even within the conception in thought itself there’s the initial and overall/abstract [thought] which is hidden internally, and [also] the later thought that flows from the internal which is expressed as speech or action. (This is the knowledge that unfolds within the personality characteristics19Heb.: mee-dote—which can also be understood as the lower seven s’feerote..) And it [emphatic] is recognized as the effect of action or in speech (which is action). But the earlier internal thought is impossible to express as speech, as in the context of “honey and milk under your tongue” (refer to Chageega 13a [for more details]). And that is the supernal knowledge, as per the context of “a person can’t understand his teacher…” (Avoda Za-ra 6b): that a student can’t grasp it unless his teacher illuminates the subject to a scholar who is then capable of understanding on his own. All of this are about thoughts in a person’s heart/mind, but in reference to Him (blessed be His name), for whom “My thoughts are not your thoughts” (Yeshayahu 55:8)—no one can conceive in any manner the general form of His thoughts, even supernal beings. And it’s only His thoughts that unfold to accomplish His actions that are recognizable from His action by each prophet depending on their level. And this is “and you shall observe et my back”, the “et” meaning to include the thought that unfolds to accomplish the action. And it is recognizable via the power of His actions, and it is described relative to the action. “And you will not see My face”—even via the powers of His actions, which come later than what precedes them, (and per the lessons about the word yeir-oo).