Introduction
Chiasmus is a topic which fascinates Bible scholars. Most simply and broadly understood, chiasmus , or chiasm, denotes a sequence of textual units that intentionally exhibit a semantic or poetic symmetry. A clear chiastic example in English is JFK’s adage (with corresponding textual units in the same color):

Ask not what your country can do for you,

but what you can do for your country.

The name derives from the Greek letter \chi , ‘chi’, which looks like an English ‘X’ and is used to illustrate the structure of a chiasmus: e.g. ABB’A’, as shown in Table 1 . Chiasmi may be even or odd (i.e. having an unpaired distinct center), and may have an arbitrary number of lines.

While chiasmus in English is associated with high oratory skill Bothwell et al. ( 2023 ) , it is exceedingly rare as a rhetorical device in modern language:
English experts trawling through a corpus of Winston Churchill’s works found only seven chiasmi out of a total of \sim 200 speeches Dubremetz and Nivre ( 2015 ) .
However, chiasmus is extremely common in ancient literature and oratory Welch ( 1981 ) . It has been known to be a common rhetorical feature of Ancient Hebrew poetry since the 1740s Lowth ( 1839 ) .

While most scholars agree that chiasmus is a facet of Ancient Near Eastern writings, there is much debate about its prevalence, purpose, and location.
Biblical scholars have proposed its use to underscore characterization in narrative passages Assis ( 2002 ) , as a poetic device in the Psalms Martin ( 2018 ) , and to capture ritualistic language in legal documents McCoy ( 2003 ) . However, a lack of quantitative methods for Biblical chiasmus renders the task of detection a laborious and subjective one. We provide a straightforward method to computationally formalize and detect chiasmi.

Unlike previous work which utilized handcrafted features and a log-linear model to detect fine-grained instances of chiasmus in English prose Dubremetz and Nivre ( 2017 ) , we use a statistical method based on cosine distance from line-level embedded representations of text. The use of embeddings instead of only lemmata allows us to include semantic information between lines that form a chiastic structure, enabling a more nuanced definition of chiasmus in line with rhetorical intention. This approach is supported by recent work in rhetorical device detection Schneider et al. ( 2021 ) , and includes the repetition of words, phrases, grammatical structures, or (identical or antithetical) concepts as part of the chiastic parallels. In contrast with Schneider et al. ( 2021 ) , our method is extensible to various sizes of chiasmus; that is, those of just four lines long or of 100 lines long, and is language-agnostic, whereas previous work has focused only on fine-grained, intra-line chiasmus in English or German. In this study, we analyze both half-verses and verses as units so that a chiasmus within the same verse can also be captured (i.e. “The Sabbath was made for man, not man for the Sabbath”). We formalize the notion of Biblical chiasmus thoroughly in § ˜ 2.2 .

Our main contributions are as follows:

We show that multilingual embedding spaces may be effectively used to detect rhetorical phenomena such as chiasmus in ancient manuscripts.

We provide, for the first time, a mathematical formalism of Biblical chiasmus and provide a computational algorithm for its detection.

Our method is computationally efficient and achieves robust results, with high inter-annotator agreement and system precision@ k of 0.80 at the verse level and 0.60 at the half-verse level.

We contribute to Classics and Biblical Studies by providing a qualitative analysis of the distribution of detected chiasmi, along with selected examples that highlight the effectiveness of our approach.