Shi'ur Qomah (The Measure of the Body)

About Shi'ur Qomah (The Measure of the Body)

Shi'ur Qomah, the Measure of the Body, is the most controversial single text in the entire corpus of Jewish mystical literature. A short work belonging to the Heikhalot tradition of late antiquity, it presents what claims to be a precise account of the dimensions of the body of God — the height of the divine head, the length of the divine arms, the breadth of the divine shoulders, the names of the various members of the divine body — given in cosmic measurements that defy ordinary comprehension. The shortest of the divine fingers is said to measure tens of thousands of parasangs, where each parasang is itself defined in terms vastly larger than any earthly measurement, so that the total dimensions of the divine body run into figures of staggering magnitude. The text is presented as a revelation transmitted by Rabbi Yishmael ben Elisha and Rabbi Akiva, the two great visionary rabbis around whom much of the Heikhalot literature is constructed, and is framed as a teaching that grants tremendous spiritual benefit to the practitioner who studies it: long life in this world, a place in the world to come, and protection from various dangers.

The book exists in several recensions and is preserved in some of the same medieval Ashkenazi manuscripts that preserve Heikhalot Rabbati and Heikhalot Zutarti. Martin Cohen produced the standard scholarly edition (The Shi'ur Qomah: Liturgy and Theurgy in Pre-Kabbalistic Jewish Mysticism, University Press of America, 1983; The Shi'ur Qomah: Texts and Recensions, Mohr Siebeck, 1985), printing the principal recensions in parallel and providing the first comprehensive analysis in English of the text's variants. Peter Schäfer's Synopse zur Hekhalot-Literatur (Mohr Siebeck, 1981) includes Shi'ur Qomah material in its parallel-column presentation of the Heikhalot manuscripts and uses the standard Synopse paragraph numbering for cross-reference.

The dating of Shi'ur Qomah is bound up with the broader debate about the date of the Heikhalot literature as a whole. Gershom Scholem, in Major Trends in Jewish Mysticism and in Jewish Gnosticism, Merkabah Mysticism, and Talmudic Tradition, argued for a relatively early date — perhaps the second to fourth centuries CE — and saw Shi'ur Qomah as preserving authentic traditions of Tannaitic and Amoraic mystical speculation about the form of God. The traditions reached, on Scholem's reading, back into the period of the great rabbinic figures whose names are attached to the text. David Halperin, in The Faces of the Chariot (Mohr Siebeck, 1988), challenged this dating and argued for a much later composition, perhaps the seventh or eighth century, in late-antique Babylonia. Peter Schäfer's middle position treats the text as multi-layered, with material of varying antiquity bound together in the manuscript tradition. Most current scholarship places the composition of Shi'ur Qomah somewhere between the third and the eighth centuries CE, with subsequent reworking in the early Islamic period and again by the Hasidei Ashkenaz of medieval Germany who preserved the text.

The reception of Shi'ur Qomah in the medieval period was extraordinarily controversial. Saadia Gaon, the great tenth-century Babylonian rationalist philosopher, treated the book as suspect and refused to accept its account of the divine body as literal — interpreting it instead as an allegorical or symbolic representation of God's incomparable greatness. Maimonides, in his Guide of the Perplexed and in a famous responsum, condemned Shi'ur Qomah outright as a forgery composed by a Greek preacher and declared that it should be burned. The condemnation was driven by Maimonides's deep philosophical commitment to the absolute incorporeality of God and his horror at any text that seemed to attribute body, dimension, or measurement to the deity. The condemnation had a major effect on the subsequent transmission of the text: copies were destroyed, references in standard works were censored, and the book disappeared from mainstream Jewish circulation for centuries. It was preserved largely by Kabbalistic and pietistic circles — the Hasidei Ashkenaz, the early theosophical Kabbalists of Provence, and later the Kabbalists of Castile — who continued to copy it and to interpret its dimensions allegorically rather than literally.

The literary form of Shi'ur Qomah is striking and difficult. The text presents a series of statements about the divine body in a stark and rhythmic style: "The height of his head is so-and-so many parasangs, and its name is so-and-so. The length of his right arm is such-and-such, and its name is such-and-such." Each member of the body is given both a measurement and a name, and the names are typically not ordinary Hebrew words but strings of letters that appear to be theurgic constructions of some kind — divine names whose letters and syllables encode further mystical meanings. The cumulative effect of reading the text is overwhelming: the practitioner is presented with a vision of God whose dimensions exceed any conceivable scale, whose body is composed of celestial substances, and whose every member bears a secret name whose recitation has theurgic power.

Whether the dimensions of Shi'ur Qomah were ever intended literally is among the central interpretive questions of the text. Scholem, in his early work on the book, argued that the dimensions were meant literally — that the author or authors of Shi'ur Qomah believed that God had a body, that the body had measurements, and that the text was reporting those measurements as a matter of fact. Later scholars, including Cohen, Schäfer, and Elliot Wolfson, have tended toward more nuanced readings: that the literal language of the text serves a theurgic or visionary purpose, that the cosmic dimensions are a way of asserting God's incommensurability with any earthly measure, that the names attached to the divine members are the real point of the text and the dimensions are largely a frame for the names. The question of literal versus symbolic interpretation has been debated for over a thousand years, beginning with Saadia and Maimonides, and continues in contemporary scholarship without final resolution.

The book's transmission through the Hasidei Ashkenaz of twelfth- and thirteenth-century Germany was decisive for its survival. The Kalonymide circle of Worms, Speyer, and Mainz preserved Shi'ur Qomah along with the rest of the Heikhalot corpus and incorporated its imagery and theurgic practice into their own pietistic system. Eleazar of Worms, the leading figure of the school, drew heavily on Shi'ur Qomah's lists of divine names in his own works on the names of God. Through the Hasidei Ashkenaz the text passed into the broader stream of medieval Kabbalah, where it became one of the sources for the Kabbalistic doctrine of the divine body and the system of parzufim (divine personae) that would reach its full development in Lurianic Kabbalah of the sixteenth century.

Content

Shi'ur Qomah is a short text — depending on the recension, between a few thousand and perhaps ten thousand words — and is structured around two main components: the dimensions of the divine body and the names of its members.

The opening framing presents the text as a teaching transmitted by Rabbi Yishmael ben Elisha and Rabbi Akiva. The opening sections emphasize the spiritual benefits of studying the text: long life, a place in the world to come, and protection from various dangers. Some recensions also include warnings about the danger of the practice and prescriptions for the ritual purity required of the practitioner. The framing material draws on the same conventions that structure the rest of the Heikhalot literature, and the connection to Akiva and Yishmael is part of the broader Heikhalot strategy of grounding the practice in Tannaitic authority.

The dimensions of the divine body form the central content of the text. Shi'ur Qomah presents a systematic account of the height of God's head, the breadth of his shoulders, the length of his arms and legs, the size of his fingers and toes, and so on through every member of the divine anatomy. The measurements are given in cosmic units (parasangs of unimaginable length, divided into still smaller units that are themselves vast) and the cumulative figures run into magnitudes that exceed any earthly scale. The shortest divine finger is said to measure tens of thousands of parasangs, the divine head is described in terms that defy human imagination, and the total height of the divine body is presented as something that no human mind can grasp. Whether these dimensions were intended literally or as a way of asserting God's incommensurability with any creaturely measure has been debated for over a thousand years.

The names of the divine members form the second main component. Each part of the divine body is given a secret name, and these names are not ordinary Hebrew words but strings of letters that appear to be theurgic constructions — divine names whose letters and syllables encode further mystical meanings. The names are presented as having power: the practitioner who knows them has access to the parts of the divine body they designate, and the recitation of the names has theurgic effect. The lists of names in Shi'ur Qomah parallel the lists of divine names in Heikhalot Zutarti and in the magical literature of Sefer HaRazim, and the relationship between Shi'ur Qomah's names and the broader Jewish tradition of theurgic name speculation is one of the central concerns of recent scholarship on the text.

The visions of glory form a less prominent but real component. Some passages of Shi'ur Qomah describe the divine king on his throne, surrounded by his angelic hosts, in language that recalls the throne visions of Heikhalot Rabbati and Heikhalot Zutarti. The body of the divine king is described as if it were itself a vast landscape — composed of celestial substances, illuminated by divine light, surrounded by the four living creatures of Ezekiel's vision and by countless ranks of angels. These visionary passages link Shi'ur Qomah to the broader Heikhalot tradition and show that the dimensions and names are embedded in a larger imaginative world.

The benedictory closing material in some recensions promises that the practitioner who reads the text, masters its dimensions, and recites its names will be granted long life, success in worldly affairs, protection from harm, and a place in the world to come. The benedictions function as both promise and warning — they describe the rewards of proper study and the punishments of improper or unworthy practice — and they serve to authorize the text as a legitimate object of spiritual attention.

The textual relationships among the various recensions of Shi'ur Qomah are complex. Cohen's edition prints what he identifies as the principal recensions in parallel; Schäfer's Synopse includes Shi'ur Qomah material in its broader presentation of the Heikhalot manuscripts. No single recension is universally accepted as primary, and the text exists in the manuscript tradition as a constellation of related but distinct versions whose interrelationships are still imperfectly understood.

Key Teachings

The central teaching of Shi'ur Qomah, on its surface, is that God has a body whose dimensions can be measured and whose members can be named. The text presents this teaching not as speculation but as revelation, framed as the transmission of secret knowledge from Rabbi Akiva and Rabbi Yishmael, and supported by the cosmic magnitude of the measurements and the elaborate structure of the divine names. The reader who takes the text at face value confronts a vision of the divine that is radically anthropomorphic in form even as it is radically incommensurable in scale — a God whose body resembles a human body in its general organization but whose dimensions exceed any conceivable creaturely magnitude.

A second teaching, more easily extracted from the text by allegorical or symbolic reading, is that God is incomparably greater than any earthly measure. The cosmic dimensions of Shi'ur Qomah serve, on this reading, to assert the absolute transcendence of God by piling up measurements that defeat the imagination — not to claim that God has literal dimensions but to claim that any attempt to measure God necessarily produces figures of incomprehensible magnitude. This reading was favored by Saadia Gaon and by the medieval and early modern interpreters who wished to preserve the text without endorsing literal divine corporeality.

A third teaching is the doctrine that each member of the divine body bears a secret name whose recitation has theurgic power. The names of Shi'ur Qomah, like the divine names of Heikhalot Zutarti and Sefer HaRazim, are presented as instruments of practice rather than as theological labels. The practitioner who knows the names of the divine head, the divine arms, and the divine fingers has access to the corresponding parts of the divine body and can use that access for spiritual benefit. This conception of divine names as theurgic instruments runs through the entire Jewish mystical and magical tradition of late antiquity and the Middle Ages and finds in Shi'ur Qomah a particularly concentrated expression.

A fourth teaching, less explicit but real, is the doctrine that mystical experience is fundamentally a vision of God — not merely an experience of God's presence or a unification with God's essence, but a literal vision of the divine king on his throne, his body, his face, his glory. The Heikhalot literature as a whole is a literature of visionary experience, but Shi'ur Qomah pushes this conviction to its limit by claiming that the body of God can itself be the object of visionary contemplation. The text represents the most extreme form of the visionary impulse in Jewish mysticism and stands at the opposite pole from the apophatic and unitive mysticism that would later be developed in the Lurianic and Hasidic traditions.

A fifth teaching is the spiritual reward of study itself. Shi'ur Qomah promises that the practitioner who reads the text, masters its dimensions, and recites its names will be granted long life, worldly success, protection from harm, and a place in the world to come. This is not the promise of mystical experience as such but the promise of practical reward for the act of engaging with the text. The teaching reflects a religious sensibility in which sacred texts are not merely sources of information but channels of divine power, and the act of reading them is itself a sacrament.

Translations

Shi'ur Qomah has been translated only partially into English, and the standard scholarly resources are in Hebrew and German. The translation history reflects the controversial status of the text and the difficulty of its content.

Martin Cohen produced the foundational scholarly edition in two volumes: The Shi'ur Qomah: Liturgy and Theurgy in Pre-Kabbalistic Jewish Mysticism (University Press of America, 1983) and The Shi'ur Qomah: Texts and Recensions (Mohr Siebeck, 1985). These works print the principal Hebrew recensions of the text, provide English translations of substantial portions, and offer extensive commentary on the dimensions, names, and interpretive history. Cohen's edition is the indispensable starting point for any serious study of the text in English.

Peter Schäfer's Synopse zur Hekhalot-Literatur (Mohr Siebeck, 1981) prints Shi'ur Qomah material in parallel with the other Heikhalot manuscripts and uses the standard Synopse paragraph numbering. Schäfer's Übersetzung der Hekhalot-Literatur (Mohr Siebeck, 1987-1995) provides a German translation of the entire Heikhalot corpus, including the Shi'ur Qomah material, organized by Synopse paragraph numbers.

In English, James Davila's Hekhalot Literature in Translation: Major Texts of Merkavah Mysticism (Brill, 2013) translates Shi'ur Qomah passages along with the other Heikhalot literature. Davila's translation is based on the Synopse and is the most accessible complete English rendering of the Heikhalot corpus.

Earlier scholarly treatments include those of Gershom Scholem in Major Trends in Jewish Mysticism (Schocken, 1941) and Jewish Gnosticism, Merkabah Mysticism, and Talmudic Tradition (Jewish Theological Seminary, 1960), which include translations of key passages with commentary. Joseph Dan included Shi'ur Qomah material in his anthologies of early Jewish mysticism. Elliot Wolfson's Through a Speculum That Shines: Vision and Imagination in Medieval Jewish Mysticism (Princeton, 1994) discusses Shi'ur Qomah at length and translates several key passages with detailed interpretive commentary.

The book has not received the kind of widely distributed translation that Sefer Yetzirah has received in Aryeh Kaplan's edition, in part because of its difficult content and in part because of the controversies surrounding its theological status. Serious students will need to work with Cohen's edition and Davila's translation in tandem.

Controversy

Shi'ur Qomah has been controversial since the medieval period, and the controversies surrounding the text have shaped its transmission, its interpretation, and its place within Jewish thought.

The first major controversy is the question of whether the text's dimensions of the divine body were intended literally. Saadia Gaon, the great tenth-century Babylonian rationalist, treated the text with suspicion and refused to accept its account of the divine body as literal — interpreting it instead as an allegorical or symbolic representation of God's incomparable greatness. Maimonides, in his Guide of the Perplexed and in a famous responsum, condemned Shi'ur Qomah outright as a forgery composed by a Greek preacher and declared that it should be burned. The condemnation was driven by Maimonides's deep philosophical commitment to the absolute incorporeality of God and his horror at any text that seemed to attribute body, dimension, or measurement to the deity. Maimonides's condemnation had a major effect on the subsequent transmission of the text: copies were destroyed, references in standard works were censored, and the book disappeared from mainstream Jewish circulation for centuries.

The second major controversy is the question of dating. Gershom Scholem argued for an early date, perhaps the second to fourth centuries CE, and saw Shi'ur Qomah as preserving authentic Tannaitic and Amoraic traditions about the form of God. David Halperin in The Faces of the Chariot challenged this dating and argued for a much later composition, perhaps the seventh or eighth century, in late-antique Babylonia. Peter Schäfer's middle position treats the corpus as multi-layered, with material of varying antiquity bound together in the manuscript tradition. Most current scholarship places the composition somewhere between the third and the eighth centuries CE.

The third major controversy concerns the relationship between Shi'ur Qomah and the broader Heikhalot literature. Some scholars treat the text as integral to the Heikhalot corpus and read it as a particular development of the same visionary impulse that produced Heikhalot Rabbati and Heikhalot Zutarti. Others treat Shi'ur Qomah as a distinct tradition that was secondarily attached to the Heikhalot literature in the manuscript transmission. The fact that Shi'ur Qomah focuses entirely on the body of God, with little of the ascent narrative that structures the rest of the Heikhalot corpus, supports the latter view; the fact that it shares manuscripts, vocabulary, and visionary concerns with the rest of the corpus supports the former.

A fourth controversy concerns the influence of Shi'ur Qomah on Christian and Islamic theology and on the broader history of late-antique and early medieval anthropomorphism. Some scholars (notably Idel and Wolfson) have argued that the text was known to early Christians and influenced certain strands of Christian mysticism that took seriously the doctrine of the imago Dei (the image of God in humanity); others have been more skeptical of these connections. The relationship between Shi'ur Qomah and early Islamic anthropomorphic theology — the Mujassima or "corporealists" — has also been debated, with some scholars seeing direct influence and others seeing parallel developments without contact. The polemical literature against the Mujassima in early Islam contains references to Jewish anthropomorphic doctrines that have sometimes been read as references to Shi'ur Qomah, though the identification is not certain. What is clear is that the question of divine corporeality was a live issue across the religious traditions of the late-antique and early medieval Mediterranean and that Shi'ur Qomah was the Jewish text most explicitly committed to a strong version of the doctrine.

Influence

The influence of Shi'ur Qomah on Jewish thought has been deep but largely subterranean. The text has rarely been openly endorsed in mainstream Jewish theology, but its imagery and its theurgic apparatus have shaped the Jewish mystical imagination from late antiquity to the present.

The most direct influence is on the Hasidei Ashkenaz of twelfth- and thirteenth-century Germany. The Kalonymide circle of Worms, Speyer, and Mainz preserved Shi'ur Qomah and incorporated its imagery into their own mystical and pietistic system. Eleazar of Worms drew heavily on Shi'ur Qomah for his own works on the divine names and the structure of the divine glory, and his treatises on the Sod ha-Yichud (the Mystery of Unity) and the divine kavod (glory) bear the unmistakable stamp of the Shi'ur Qomah tradition. Without the Hasidei Ashkenaz, Shi'ur Qomah would have been lost; through them, it passed into the broader stream of medieval Jewish mysticism.

Through the Hasidei Ashkenaz, the text influenced the theosophical Kabbalah of Provence and Spain. The Sefer HaBahir, the first major text of medieval Kabbalah, treats the sefirot in language that owes something to the Shi'ur Qomah tradition's concern with the structured anatomy of the divine. The Zohar, in its long passages on the Idra Rabbah and the Idra Zutta — the "great assembly" and "lesser assembly" sections that describe the body and face of the Holy Ancient One — develops a theology of the divine body that is directly indebted to Shi'ur Qomah. The Lurianic doctrine of parzufim (divine personae or "faces") that organizes the divine emanation into anthropomorphic configurations of Father, Mother, Son, and Daughter is the most elaborate descendant of the Shi'ur Qomah tradition in the Jewish mystical canon.

The book also influenced the Jewish liturgical tradition, though the influence is more difficult to trace. Several piyyutim of the medieval period contain language describing the divine glory in terms that recall Shi'ur Qomah, and the broader synagogue tradition of imagining God enthroned in glory — surrounded by his angelic hosts, his face turned toward Israel — shares with Shi'ur Qomah a willingness to use anthropomorphic language even while insisting in principle on the incorporeality of God.

The book has had a complicated legacy in modern Jewish thought. The rationalist tradition descending from Maimonides has continued to find Shi'ur Qomah embarrassing, while the mystical tradition has continued to interpret it allegorically or to treat it as evidence for the depth and antiquity of the Jewish visionary tradition. Gershom Scholem's rehabilitation of the Heikhalot literature in the twentieth century brought Shi'ur Qomah back into scholarly view, and Martin Cohen's editions and Elliot Wolfson's interpretive work have made the text a central object of contemporary research on Jewish mysticism.

In the wider history of religious imagination, Shi'ur Qomah is significant as a witness to a sensibility that takes the visualization of God seriously. Such sensibilities are unusual in monotheistic traditions, which typically forbid the depiction of God altogether, and Shi'ur Qomah stands as an important counterexample to the assumption that monotheism necessarily entails the absolute non-visualization of the deity.

Comparative scholars have placed Shi'ur Qomah alongside the anthropomorphic theology of certain early Christian and early Islamic traditions, alongside the Hindu and Tibetan traditions of visualizing the body of the deity in tantric meditation, and alongside the Buddhist Mahayana traditions of Buddha-bodies (the trikaya doctrine of nirmanakaya, sambhogakaya, and dharmakaya). The comparisons are not always tight, but the recurrent impulse to visualize the divine in bodily form, even in traditions that on the surface forbid such visualization, points to something deep in the religious imagination of human beings. Shi'ur Qomah is the Jewish contribution to this comparative file, and its dimensions and names take their place alongside the elaborate visualizations of other contemplative traditions as variations on a single human impulse to see what cannot be seen.

Significance

Shi'ur Qomah occupies a particular position in the history of Jewish thought because it forces a confrontation with a basic theological question: whether God has a body. The mainstream Jewish philosophical tradition, from Saadia and Maimonides through the modern era, has insisted on the absolute incorporeality of God and has treated any attribution of body or dimension to the deity as a serious theological error. Shi'ur Qomah, on its surface, appears to violate this principle in the most flagrant possible way: it not only attributes a body to God but provides precise measurements of every member of that body and assigns each member a secret name. The text is therefore a permanent challenge to the rationalist consensus of medieval and modern Jewish theology and a witness to a strand of the tradition in which the corporeality of God was at least imaginable, perhaps even thinkable, perhaps even practiced as a focus of meditation.

The book's significance for the history of Jewish mysticism lies in its preservation of an extreme version of the visionary tradition. Where Heikhalot Rabbati and Heikhalot Zutarti describe the ascent through the palaces and the encounter with the throne, Shi'ur Qomah focuses entirely on the body of the divine king who sits upon the throne. It is the most intense and concentrated expression in any surviving Jewish source of the conviction that God can be visualized, contemplated, and (in some sense) seen — a conviction that runs through the Heikhalot literature as a whole but reaches its purest form in Shi'ur Qomah.

The book's significance for the later history of Kabbalah is also large. The Kabbalistic doctrine of the divine body — the system of correspondences between the parts of the human body and the parts of the divine — has roots in Shi'ur Qomah. The Lurianic doctrine of parzufim (divine personae or "faces"), in which the divine emanation organizes itself into anthropomorphic configurations of Father, Mother, Son, and Daughter, is a distant descendant of the Shi'ur Qomah tradition. The Kabbalistic practice of contemplating the sefirotic tree as if it were a human body, with the head at Keter and the feet at Malkhut, draws on the same impulse that produced Shi'ur Qomah's measurements of the divine head, arms, and legs.

The book is also significant as a flashpoint in the long history of Jewish theological debate. Saadia's discomfort, Maimonides's outright condemnation, and the medieval Karaite polemics against the rabbinic tradition all turned on the question of how to interpret Shi'ur Qomah. The book has thus served as a kind of Rorschach test for Jewish theology: rationalists have wanted to dismiss it, mystics have wanted to preserve it, philosophers have wanted to allegorize it, and the practical question of what to do with it has shaped the boundaries of acceptable Jewish thought for over a millennium.

Connections

Shi'ur Qomah is one of the central texts of Heikhalot literature and an important document of Merkavah mysticism. Its focus on the body of the divine king complements the Heikhalot literature's broader concern with the ascent through the palaces and the vision of the throne.

The book is closely tied to Rabbi Akiva and Rabbi Yishmael ben Elisha, the two Tannaitic sages who serve as its narrative authorities. The attribution links Shi'ur Qomah to the same circle that the Heikhalot tradition treats as the origin of all visionary practice.

It stands in close relationship to the other major Heikhalot texts, particularly Heikhalot Rabbati and Heikhalot Zutarti, with which it shares manuscripts, vocabulary, and visionary concerns. The four texts together — Rabbati, Zutarti, Shi'ur Qomah, and Maaseh Merkavah — form the core of the Heikhalot corpus.

The book is connected to Sefer Yetzirah through their shared interest in the cosmic and the linguistic dimensions of the divine, though Shi'ur Qomah focuses on the body of God where Sefer Yetzirah focuses on the letters and sefirot.

The text was preserved by the Hasidei Ashkenaz of twelfth- and thirteenth-century Germany. Eleazar of Worms drew heavily on Shi'ur Qomah for his own works on the divine names and the structure of the divine glory. Through the Hasidei Ashkenaz the book passed into the broader stream of Kabbalah, where it became one of the sources for the doctrine of the divine body that runs through medieval and early modern Jewish mysticism.

The book also stands in tension with the rationalist Jewish philosophical tradition. Saadia Gaon treated it with suspicion, and Moses Maimonides condemned it outright as a forgery and declared that it should be burned. The controversy over Shi'ur Qomah was a central episode in the medieval debate about the nature of God and the legitimacy of mystical literature within the Jewish canon, and it helped define the boundaries between rationalist and mystical strands of Jewish thought.

In the later Kabbalistic tradition, Shi'ur Qomah's vision of the divine body fed into the Lurianic doctrine of parzufim (divine personae or "faces") that Isaac Luria developed in sixteenth-century Safed and that Chaim Vital recorded in the Lurianic gates. The system of anthropomorphic divine emanations elaborated by Luria represents in some respects a sophisticated philosophical reworking of the older Shi'ur Qomah tradition.

Further Reading