The act of Tzimtzum.
The Tzimtzum is the willful self-restriction by which Eyn Sof made a finite cosmos possible. Localised in one of His powers, by choice, calibrated to the goal.
Op. 24 is Klach's central cosmogonic chapter. After 23 chapters of structural foundation — what God's Will is, what the Sefirot are, what the letters and Names execute — Op. 24 finally asks the question the foundation requires: how did a finite cosmos ever come into being, given Eyn Sof's limitlessness? The answer is the Tzimtzum, given here in its full operational definition.
Three claims, all in Op. 24.
Localised. The Tzimtzum is in one of Eyn Sof's limitless powers — the power that bestows good on creatures outside Himself. All His other limitless powers remain unaffected. This is critical. The Tzimtzum is not a global change in Eyn Sof's being; it is a specific restriction in a specific power, set up so that the bestowal of Op. 3 can operate. Eyn Sof has not become smaller or weaker; He has willfully restricted one specific aspect of His operation.
Willful. The Tzimtzum is not necessity but choice. Eyn Sof acts not in His omnipotence but with precisely the calibrated power needed for the goal. This is the cosmic counterpart to Op. 14's exactly required configuration. The contraction is exactly what the bestowal-plan required, no more and no less, by His choice.
A path of limited action. What was previously hypothetical — the pathway of limitation, subsumed in Eyn Sof as a negated possibility — is now revealed in actuality. The Tzimtzum is not just the absence of limitlessness; it is the positive act that sustains the realm of limits in being. Limitation, before the Tzimtzum, was only a possibility within the limitlessness; after the Tzimtzum, it is an actual realm in which the bestowal can operate.
The chapter's central analogy: limitlessness includes limitation in the way life includes death — by negating it. The Tzimtzum is the moment at which the negated possibility becomes actual. Death is real because life made it so by negation; limitation is real because limitlessness, in the act of Tzimtzum, made it so by negation.