Wednesday, December 3, 2025

Two Hearts in One Chest?

“Two Hearts in One Chest?”

A Theological and Scientific Appraisal of Qur’an 33:4

By Dr. Maxwell Shimba — Shimba Theological Institute, New York, NY

Abstract

Qur’an 33:4 states that God “has not placed two hearts in any person’s chest.” Read straightforwardly, the verse appears to make an empirical claim about human anatomy, while the classical exegetical tradition typically treats it as a rhetorical denial aimed at Arab idioms and certain pre-Islamic practices. This article evaluates the verse on two fronts: (1) its literary-historical intent and the range of traditional interpretations; and (2) the biological record on “two hearts,” from human anomalies and surgical cases to animals with multiple cardiac pumps. I then pose a series of theological and scientific questions intended to sharpen debate across confessional lines and to clarify what, exactly, the verse is—and is not—asserting.

1) Text and Immediate Context

Qur’an 33:4 (Al-Aḥzāb) in a widely used modern English rendering reads:

“Allah does not place two hearts in any person’s chest; nor does He regard your wives as your mothers [by your saying ‘you are as my mother’s back’], nor your adopted sons as your [biological] sons…” (Quran.com)

Classical and modern tafsīr link 33:4–5 to two reforms: (a) invalidating ẓihār (a pre-Islamic formula likening a wife to one’s mother to dissolve marital obligations) and (b) correcting adoption/naming customs associated with Zayd ibn Ḥāritha, whose case is further discussed in 33:37. (QuranX, Islam Stack Exchange, Yaqeen Institute for Islamic Research)

Notably, al-Jalālayn says the opening clause refutes those who boasted they had “two hearts” (i.e., superior intellect/resolve), situating the line as a rhetorical denial rather than a literal foray into anatomy. Maudūdī’s Tafhīm likewise reads it as an emphatic negation placed alongside the reforms of ẓihār and adoption. (QuranX, Surah Quran)

2) Linguistic Considerations

The verse says “God has not placed two hearts in any man/person (min rajulin) within his chest.” On its face, it universalizes to any human. Yet in idiomatic Arabic, “two hearts” functioned as a figure of speech for divided allegiance or an alleged mental superiority. Thus, the line plausibly means: a person cannot be of two minds in ultimate loyalty, dovetailing with the adjoining legal-ethical reforms. This reading is consistent with major tafsīr. (QuranX, Quran.com)

Still, because the verse uses concrete anatomical wording, questions arise about scope: Is the statement (a) purely idiomatic; (b) a generalization about natural human anatomy; (c) a theological axiom about undivided devotion; or (d) more than one of these at once?

3) Biology: What Do We Know about “Two Hearts”?

3.1 Humans

  • Naturally occurring two complete hearts in a single human being (from conception) is not a recognized viable phenotype in medical literature. Congenital anomalies can produce complex hearts (incorrect chambering, duplication of parts, situs disorders), but not a fully duplicated, independent second heart. (Circulation Journals, Translational Pediatrics)

  • Conjoined twins can present with two hearts within a shared thoracic complex, but that is two individuals biologically. (This article focuses on single individuals.)

  • Heterotopic heart transplantation (a “piggy-back” procedure) can result in one patient living with two hearts (the native and the donor heart) functioning simultaneously for years or decades—a medical reality since the late 20th century. Clinicians and case reports explicitly describe “living with two hearts.” (Temple Now, PMC, Oxford Academic)

Implication: If 33:4 were read as a strict, timeless anatomical claim, heterotopic transplants form an interesting boundary case: a single person with two functional hearts in one chest by medical intervention.

3.2 Animals

Multiple “hearts” (or heart-like pumps) do occur in other species:

  • Octopuses and squids: typically three hearts—one systemic heart and two branchial hearts that pump blood across the gills. (Natural History Museum)

  • Hagfish: one principal heart plus several accessory pumps (some accounts enumerate up to five “hearts” when counting auxiliaries). (The Lancet, Labroots)

  • Earthworms: often misdescribed as having “five hearts,” but these are aortic arches—contractile vessels, not homologous to a vertebrate heart. (CK-12 Foundation, A-Z Animals)

Popular science outlets continue to highlight animals with multiple pumping organs, underscoring that “more than one heart” is a real, well-documented non-human adaptation. (WorldAtlas, The Times of India)

4) Theological Readings and Points of Tension

  1. Rhetorical/Idiomatic Reading (dominant in tafsīr):
    The verse negates the metaphor of dual hearts to insist upon undivided loyalty and to anchor legal reforms. On this reading, the statement is not a propositional claim about anatomy, and neither conjoined twins nor heterotopic transplants are relevant. (QuranX, Surah Quran)

  2. Literal-Anatomical Reading (minor but possible):
    If taken as a universal claim about creation, then (a) natural human development indeed does not produce two separate hearts; yet (b) modern surgery can place two hearts in one chest with both beating—raising the question whether the verse intended to preclude such a state “for any human” in principle, or speaking of how God originally fashions humans (pre-intervention). (PMC)

  3. Meta-Ethical Reading (allegiance):
    The “one heart” motif functions as a theological axiom: God does not design humans to sustain ultimate dual loyalties. This coheres with the immediate legal corrections (ẓihār, adoption naming) as acts that required cleaving false equivalences (wife ≠ mother; adopted son ≠ biological son) to restore moral clarity. (My Islam)

5) A Structured Challenge: Questions for Debate

A. Theological Questions

  1. Scope of Universality: Does “any person” (min rajulin) intend all humans across all times and conditions, or only natural formation absent postnatal intervention? How do exegetes justify one scope over the other from the Arabic and the context? (Quran.com)

  2. Genre and Intent: If the clause is rhetorical, what markers in 33:4–5 signal metaphor rather than empirical claim? How does this affect Muslim claims that Qur’anic statements routinely align with scientific discovery? (QuranX)

  3. Coherence with Reforms: In what way does “one heart” theologically underwrite the reforms on ẓihār and adoption—i.e., is the verse primarily about moral non-equivalence (you cannot treat X as if Y), rather than about biology? (Surah Quran, Yaqeen Institute for Islamic Research)

  4. Providence and Technology: If God says no person has two hearts, how should a Muslim theologian account for heterotopic transplants that produce precisely that state? Is the verse restricted to original creation (fitra), allowing technology to create exceptions, or is it timeless and exceptionless? (Temple Now, PMC)

  5. Hermeneutical Consistency: When should verses be read metaphorically versus literally? What criteria—language, context, consensus (ijmāʿ), or scientific data—decide the matter?

B. Scientific Questions

  1. Definitional Rigor: What counts as a “heart”? Vertebrate single pump vs. invertebrate multiple pumps; accessory vs. principal hearts (e.g., hagfish). How should claims about “two hearts” control for homology and function? (The Lancet, CK-12 Foundation)

  2. Human Boundary Cases: Do conjoined twins (two hearts in shared anatomy) or heterotopic recipients falsify a blanket, literal reading? If not, why not? (Temple Now, PMC)

  3. Developmental Biology: Are there any documented human cases of cardiac duplication (a truly second, independent heart) compatible with postnatal life? Current literature points to complex malformations, not full duplication. What would such a case imply for scriptural interpretation? (Circulation Journals)

  4. Comparative Physiology: Given that octopuses have three hearts and hagfish have multiple pumps, how should theology engage non-human diversity in God’s creation without retrofitting texts into scientific concordism? (Natural History Museum, The Lancet)

  5. Surgical Theology: Does the success of two-heart physiology in heterotopic transplants suggest that “two hearts” is biophysically viable for humans (with assistance), thus challenging readings that treat the state as inherently impossible? (PMC)

6) Synthesis and Position

  • Historically and exegetically, 33:4 functions as a rhetorical and ethical pivot: “two hearts” negates divided allegiance and undergirds reforms to marriage and adoption practices. This is well attested in classical tafsīr. (QuranX, Surah Quran)

  • Empirically, no naturally developed human is known to possess two fully independent hearts; however, medicine can—and does—produce a two-heart state in one chest via heterotopic transplantation, sometimes for decades. Thus, a strictly literal, exceptionless reading that outlaws the very possibility is difficult to maintain without narrowing the claim to natural formation only. (PMC, Temple Now)

  • Comparative biology demonstrates that multiple hearts are a real feature of God’s broader creation (octopus, hagfish, etc.), underscoring that the Qur’anic clause, if read as a universal biological principle, cannot extend beyond humans without qualification. (Natural History Museum, The Lancet)

7) Conclusion

A careful, scholarly reading suggests Qur’an 33:4 is best understood as rhetorical theology in service of moral-legal reform, not as a blanket scientific assertion about anatomy. Nevertheless, because the verse uses anatomical language, it invites empirical scrutiny and, with modern cardiothoracic practice, yields borderline counterexamples (two hearts in one person post-transplant). Theologically, Muslim scholars can preserve the verse’s integrity by anchoring it in idiom and intention (undivided allegiance, rejection of false equivalences), while acknowledging that medical technology can generate physiological states that the verse was not addressing. From a debate standpoint, the key is clarifying scope and genre—and resisting the urge to stretch the text into a universal scientific maxim.

Selected References

Correspondence:
Shimba Theological Institute · New York, NY

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