Smoke as Substance: Liminal Materiality in Ancient and Medieval Thought

I. Introduction: Smoke and the Problem of Matter

In the classical schema of four elements—earth, air, fire, and water—each substance was associated with particular qualities and positions within the cosmological hierarchy. Aristotle's model further organized these elements according to natural motion: earth and water moved downward; air and fire moved upward. Yet certain phenomena, especially those that emerged from combustion, resisted neat placement. Chief among these was smoke.

Neither purely air nor fire, neither fully material nor wholly immaterial, smoke occupied a strange ontological space. It was transient, visible but dissipating, produced yet untouchable. In this ambiguity, pre-scientific thinkers frequently interpreted smoke not as waste, but as a signifier—of transformation, of communication, of the porous boundary between realms. In doing so, they assigned it roles more commonly associated with the elusive “fifth element”: ether.

II. Classical Roots: Between Fire and Air

The Greeks recognized the complexity of smoke but rarely granted it elemental status. In De Caelo, Aristotle refers to smoke (kapnos) as a byproduct of combustion—an exhalation of matter consumed by fire. He classifies it alongside mist and vapor, noting its movement upward and its dependence on heat. While never described as an element in itself, smoke participates in the elemental cycle as an intermediate product, one that suggests the latent instability of the primary categories.

Roman authors, including Pliny the Elder, describe smoke in more pragmatic terms—often noting its role in ritual, agriculture, or metallurgy. However, in literary and religious contexts, smoke becomes more than nuisance: it marks sacrifice, transition, purification. The smoke of burnt offerings, rising visibly into the sky, is treated as a kind of communication with the divine. In this way, smoke comes to resemble pneuma—spirit, breath, life-force—without fully collapsing into it.

III. Alchemical and Islamic Perspectives

Alchemical traditions, especially those emerging in Hellenistic Egypt and later in the Islamic world, treat smoke with increased metaphysical seriousness. Jabir ibn Hayyan (Geber), in his works on transformation and sublimation, describes the rūḥ or "spirit" of substances as something extractable through heat, often appearing as vapor or smoke. In this frame, smoke is not mere residue but revelation—the outward sign of an internal essence being drawn out and elevated.

Islamic cosmology, influenced by both Greek and Persian sources, occasionally places smoke at the threshold of creation itself. The Qur’an (Surah 41:11) describes the early state of the heavens as “dukhan”—translated as “smoke”—from which the cosmos was formed. While interpretations vary, the imagery suggests a primordial condition of dispersal, a pre-form materiality awaiting divine structuring. This is not the smoke of incense or ash, but a metaphysical substrate—a cloudy ether before distinction.

IV. Medieval Theology and Liturgical Smoke

In Christian Europe, the symbolic valence of smoke intensified, especially in liturgical practice. Incense, a product of resinous material burned in ritual contexts, was treated not merely as sensory enhancement but as theological medium. The Ordo Romanus prescribes its use in processions, masses, and funerals, where its rising motion was understood to represent prayers ascending to God. As Psalm 141:2 states: “Let my prayer be set forth before thee as incense; and the lifting up of my hands as the evening sacrifice.”

The use of thuribles, swung in arc-like motion during liturgy, reinforced the performative aspect of smoke as spatial and temporal marker. It delineated sacred space, consecrated the body, and mediated between congregant and mystery. Though theologians did not define smoke as a substance of cosmological importance, its ritual ubiquity gave it a kind of functional ontology: an ephemeral bridge between the material and the divine.

V. Smoke as Proto-Ether

Though pre-modern thinkers lacked a unified theory of ether in the physical sense that would later develop in Enlightenment physics, they often invoked a fifth substance or principle that resembled the properties of smoke. The Stoics spoke of a divine fire or breath (pneuma) that structured the cosmos. Neoplatonists imagined an intermediary substance between form and matter. In each case, the qualities attributed to this principle—movement, permeability, subtlety—mirror those observed in smoke.

When 17th-century scientists began to theorize the luminiferous ether as the medium through which light moved, they did so in part by analogy to substances like mist and smoke: diffuse, omnipresent, invisible yet real. Smoke, long considered liminal and suggestive, became a metaphor for something more fundamental—the medium that carries force without being seen, that fills the space between.

VI. Conclusion: Residue and Revelation

Smoke is neither element nor absence. In pre-scientific systems of thought, it is a residue that reveals. It signals change, carries intention, and dissolves the visible into the invisible. Though never fully integrated into elemental taxonomies, it remained indispensable to the symbolic economy of matter—especially where ritual, cosmology, and transformation intersected.

In this sense, smoke operates as an analog to the ether long before ether had a name. It is the unseen link, the trailing presence, the whisper of form escaping substance. What evaporates leaves meaning behind.