Zur Vermeidung eines Wortirrtums: Was tätig zerstört werden soll, muß vorher ganz fest gehalten worden sein; was zerbröckelt, zerbröckelt, kann aber nicht zerstört werden.
Towards the avoidance of a piece of verbal confusion: What is intended to be actively destroyed must first of all have been firmly grasped; what crumbles away crumbles away, but cannot be destroyed. [Kaiser/Wilkins]
To avoid the solecism: Whatever is to be entirely destroyed must first be held very firmly: if something crumbles, it crumbles, but resists destruction. [Hofmann]
Both translators mark this aphorism cancelled. While I think there is something of interest in number ninety, which might have been cancelled because of cynical overtones that were not intended, here I think I can see why this aphorism was discarded.
Kafka distinguishes between two kinds of selection. One is artificial selection of something to be destroyed, while the other is a natural selection. Destruction is designated as exclusively active, which produces a reversal very characteristic of Kafka's thinking: what crumbles is immune to destruction. What falls apart of its own decrepitude or weakness can't be destroyed. So Bloch the tradesman will go on dragging out his days in court forever, while Josef K., who tries to do battle with the court, must be killed, although even then he seems to be given the opportunity to kill himself as the knife is passed to and fro between his executioners, and the killing is entirely unceremonious and unlike an official execution, carried out in a nondescript place.
Kafka seems to be intrigued by the idea that weaknesses can become strengths without ceasing to be weaknesses; weakness, failure, waiting, hestitating, all have their rights, too.
This aphorism also reminds me of the Penal Colony story, which depicts this kind of seizing and active destroying.
The problem is that there is a kind of active destruction that sweeps away old rubbish without noticing or caring what it's doing. It's a scandal, but it's also for that reason more innocent, because it isn't negating an existing thing so much as it's entirely preoccupied with presenting something new, like someone who dashes this and that off a table in order to set down a new acquisition on it and show it off.
Meanwhile, crumbling is distinct from the kind of vigilantism needed to maintain a stable identity, which can only be done by suppressing inevitable changes. Crumbling is not all that simple and unambiguous. Matter crumbles, but it remains matter and can be reorganized into something else. People crumble differently, although they don't stop being people, but, if crumbling is understood as a metaphor for the loss of some important aspect of self, then it is a way for the self to stop being the self. So matter can crumble and stay matter, while the crumbling self ceases to be a self at all.