Petach 57 ends with the following. After the vessels involved in the Shevira process “functioned as … imperfect phenomena” (Petach 54), and AV became a dominant force (Petachim 55-57), it then became necessary for 288 sparks  of holiness that remained behind after the breaking of the vessels to descend from there i.e., from the Chariot, so as to bolster and sustain the vessels that were descending in the course of the breaking process. And that was so that there wouldn’t be utter annihilation, and so that there’d be the possibility of a way of returning and being repaired instead.
As is explained in Ramchal’s comments here, this harkens back to the point made earlier on, in Petach 30, that even though God’s sovereignty was concealed, it still functioned of course. The effect of that came to manifest itself in the balancing of two opposing forces: on one level, rah had to function (so as to allow for free will, and to seem to thwart God’s Sovereignty), but it couldn’t be allowed to continue to hold sway forever, or else the world would be destroyed in the end. So, 288 means of reparation were allowed to sprinkle about in the ether, if you will, so that there’d be more than a tiny chance that all could go well eventually.
As a result of those 288 sparks, Ramchal concludes, the phenomena of this world came to be such that a single power, i.e., the Shechina, would remain so that the world wouldn’t be destroyed, God forbid, and so that what had been damaged could be repaired through this remaining power
 Quite simply, 288 is the value of the four AV’s spoken of above (i.e., 4 x 72 = 288). But there are another couple of reasons why there came to be 288 sparks specifically, all of which underscore the importance of AV in all this.
As Ramchal explains in his comments here, in fact “very many sparks … descended with the vessels …. But it became necessary to formulate a specific amount that would total 288. For if not, it would have meant either that there was no need for any specific number at all”, which would defeat the lesson to be learned about the centrality of AV, “or that all the sparks that descended would have been counted as a single one”, i.e. as a single amorphous conglomeration of all, without that same focus on AV, “or that the initial levels in each name”, i.e., the specific instance of AV, SaG, MaH, and BaN themselves “would have been counted” rather than AV itself.
(c) 2013 Rabbi Yaakov Feldman
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