Eli Rubin’s Kabbalah and the Rupture of Modernity is an ambitious and deeply learned monograph that traces the intergenerational evolution of the kabbalistic concept of ṣimṣum (divine contraction or withdrawal) across seven generations of Chabad-Lubavitch leadership. Structured in five parts—each devoted to a successive rebbe and the distinctive layer he contributed to the Chabad discourse on ṣimṣum—the book demonstrates how a single mystical concept became the conceptual spine of an entire intellectual and existential tradition. It is a striking work of philosophy, philology, and historiography. In my view, this is a particularly welcome contribution at a time when academic research on Hasidism has increasingly gravitated towards historical and sociological analysis, while sustained conceptual engagement with Hasidic thought has become ever rarer. Rubin’s work is all the more valuable because such conceptual analysis is not merely an academic exercise: a community’s theological worldview has a direct bearing on the conduct of its members’ daily lives. As Rubin himself writes: “When we ask, ‘What does ṣimṣum mean?’ we are really asking, ‘What does being mean?’ In a very literal sense, one’s entire worldview depends on how this question is answered” (8)—and, one might add, not only one’s worldview but one’s practical conduct as well. Just as a diaspora Jew with a Zionist worldview is more likely to make aliyah to Israel than one holding anti-Zionist convictions, the interpretation of ṣimṣum within Chabad carries real consequences for how adherents understand their religious obligations and daily conduct.

The book’s overarching thesis is that the meaning of ṣimṣum in Chabad thought was never static. Rather, each generation of leadership recalibrated the concept in response to new philosophical, political, and existential pressures, creating a cumulative and escalating tradition of reinterpretation. Rubin frames this escalation in dialogue with broader currents of modernity—from Cartesian dualism and German idealism through materialism and, ultimately, quantum physics—arguing that to confront ṣimṣum was always, in some sense, to confront the rupture of modernity itself.

Part I, “Being as Rupture,” examines the pre-Chabad history of ṣimṣum from its Midrashic origins through Lurianic Kabbalah and into the formative controversy between Rabbi Shneur Zalman of Liadi (Rashaz) and the Vilna Gaon (Gra). Rubin convincingly argues that this dispute was the theological axis around which Chabad crystallised its distinct identity. Rashaz’s insistence on a non-literal reading of ṣimṣum—that God’s withdrawal was a concealment rather than an absence—became the foundational axiom of Chabad thought (36–42, 45). Rubin situates this alongside the contemporaneous rise of Cartesian philosophy in Western Europe, observing that both traditions grappled with the rupture between spirit and matter, sacred and profane.

Part II, “Being as Nothing,” delves into the ontological consequences of this non-literal interpretation. If ṣimṣum is merely concealment, and God remains the only true being, does the material world exist at all? Through careful textual analysis of Rashaz’s writings and those of his disciples—Rabbi DovBer Schneuri, Rabbi Aharon of Staroselye, and the Ṣemaḥ Ṣedek—Rubin arrives at the unequivocal conclusion that Rashaz “believed the world to be real” (103). The world is “like naught” but not “naught literally” (52): its existence is wholly dependent on God, yet never reduced to illusion. In this, Rubin firmly rejects the influential reading of Chabad as espousing a hard acosmism, a position advanced by Rivka Schatz-Uffenheimer and developed more forcefully by Rachel Elior. Rubin’s conclusions align with the counter-arguments mounted by Yoram Jacobson (53), who had already challenged Elior’s thesis at length. One might feel that the considerable effort Rubin devotes to establishing this point is somewhat disproportionate given Jacobson’s prior work; yet Jacobson’s research was published in Hebrew and remains largely inaccessible to the Anglophone readership for whom this volume is intended. Rubin’s sustained English-language demonstration thus fills a genuine lacuna, even as one wishes he had drawn more extensively on Jacobson’s arguments in the body of his analysis. Rubin also draws illuminating parallels with Solomon Maimon’s coinage of the term “acosmism” (50) and the contemporaneous rise of German idealism.

Part III, “Being as Infinity,” marks the decisive turning point. Centred on Maharash (Rabbi Shmuel Schneersohn), the fourth rebbe, this section argues that he recast finite materiality as a continuous facet of God’s infinite being—a “trace” (reshimah) of primordiality that survives the rupture of ṣimṣum. This was a genuinely innovative move, and Rubin shows how it was bound up with the 1866 succession controversy between Maharash and his elder brother, Maharil. The tale of these two brothers—one the embodiment of Chabad’s conservative past, the other gifted with what Rubin aptly calls “the charisma of modernity” (115) —is amongst the most vivid and engaging passages in the book. Maharash’s materialist affirmation of the finite, Rubin argues, was not uncontroversial, and the Kopust–Lubavitch split reflected not merely institutional rivalry but a genuine ideological fissure over the ontological status of the created world.

Part IV, “Being as Innovation,” turns to Rashab (Rabbi Shalom DovBer), the fifth rebbe, who combined introspective mysticism with energetic activism. Where Maharash had emphasised ontological continuity, Rashab returned to the paradigm of rupture—but with a transformative twist. For him, ṣimṣum turns the cosmos into a creative crucible from which an entirely “new luminosity” (or ḥadash) can be elicited, exceeding even the primordial light that preceded ṣimṣum (183–185). The cosmic purpose, then, is not mere restoration but genuine innovation: the unprecedented disclosure of divine essentiality through embodied human practice. Rubin pays particular attention to Rashab’s rediscovery of malkhut as the “cosmic womb” of creative origination (173–176), and to the monumental book Samekh vav, in which these ideas receive their fullest and most systematic articulation.

Part V, “Being as Humanity,” traces Chabad’s passage through the catastrophes of the twentieth century under the leadership of Rayatz (the sixth rebbe) and Ramash (the seventh rebbe). For Rayatz, who led the movement through revolution, exile, and the early shadows of the Holocaust, ṣimṣum became a symbol of exilic darkness presaging the messianic dawn. Its purpose lay in the revelation yet to come. Ramash, who assumed leadership in 1950 amidst the wreckage of genocide, took up the more radical position that the purpose of ṣimṣum resides in the rehabilitation of the rupture itself. Drawing on quantum physics—especially the many-worlds interpretation and Heisenberg’s uncertainty principle (261–271)—Ramash developed a hermeneutics of radical synthesis, going so far as to rehabilitate the literal interpretation of ṣimṣum as a truth inhabiting a “lower world” (265). Most remarkably, Ramash argued that it is not God who rescues humanity from the darkness of ṣimṣum, but humanity that rescues God (257)—a stunning theological inversion placing the human individual at the epicentre of cosmic redemption.

The cumulative effect of Rubin’s five-part architecture is powerful. The reader witnesses an escalating conceptual drama: from rupture, through nothingness, to infinity, innovation, and finally humanity. Each rebbe adds a genuinely new dimension to the discourse on ṣimṣum, and Rubin ensures that the reader appreciates both the continuity and the discontinuity within the tradition.

Kabbalah and the Rupture of Modernity may well attract criticism from colleagues who prefer to see ideas more firmly embedded in their social and historical contexts. Such a concern is not without merit, but it should be noted that Rubin is far from indifferent to history: each of his five parts is attentive to the biographical, institutional, and political circumstances within which the successive rebbes operated. What distinguishes this book is not the absence of history but the primacy of philosophical analysis. I confess that I have sensed in recent years a certain gravitational pull within the field of Hasidic studies towards the historical and the sociological, and I feel—as a personal impression rather than a demonstrable claim—that the kind of sustained conceptual analysis of Hasidic thought exemplified by this volume provides a much-needed counterbalance, adding a soul to the body of historical and sociological scholarship that has so enriched the field.

Rubin’s book is a landmark contribution to the study of Chabad Hasidism and to Jewish Studies more broadly, and I warmly welcome it as a reminder that the philosophical depths of Hasidic literature deserve rigorous scholarly attention in their own right.