While genealogical approaches are sometimes dismissed as overly convenient shortcuts that evade systematic analysis,1 this can scarcely be said of Konrad Gaiserâs hypothesis in his 1985 study Theophrastus in Assos: Zur Entwicklung der Naturwissenschaft zwischen Akademie und Peripatos. For, at first glance, his attempt to associate Theophrastusâ De igne with the period between 347 and 345â¯BCE, when Aristotle and other leading Academics took refuge at the court of Hermias of Atarneus appears nothing short of paradoxical. The seemingly prosaic concerns addressed by the treatise, such as why âthe belly melts coinsâ,2 seem to be at odds with the intellectual character ascribed to this phase of Aristotelian thought in Werner Jaegerâs seminal book Aristoteles: Grundlegung einer Geschichte seiner Entwicklung.3 For Jaeger, the Assos period was one of intellectual flourishing, characterised by the discussion of abstract principles and their connection to the physical realm. This atmosphere stands in stark contrast to the widespread interpretation of Theophrastusâ De igne as a rejection of metaphysical reasoning in favour of a purely physical system, an exegetical tradition from which Gaiser decisively departs.4 The present article sets aside broader questions about the validity of the genealogical approach, focusing instead on whether there are any heuristic benefits to be gained from drawing a connection between Theophrastusâ De igne and Aristotleâs time in Assos. According to Jaegerâs division of Aristotleâs philosophical career, the Assos period is typically linked to an internal Academic debate about the elementary principles. If we follow Jaegerâs reconstruction, the lost dialogue De philosophia,5 Book A of the Metaphysics6 and the first two books of De caelo7 can be attributed to Aristotleâs time in Assos, which belongs to âthe most productive epoch in Aristotleâs lifeâ.8 Within this framework, it is possible to identify three paradigmatic features:
-
Aristotelianism was not yet fully formed, but emerged from a complex relationship with Platonism. At this stage, the break had not yet been fully consummated through the establishment of a rival school explicitly acknowledging this rupture.9 The Elegy to Eudemus, which includes a tribute to Plato, encapsulates the ambivalence of this period.
-
The focus was on critiquing Platonic ideas rather than elaborating a new philosophical school.10 For this reason, Aristotle devoted special attention to Platoâs critique of the Presocratics and assigned a prominent place to a discussion of the Timaeus.11 The latter work was read as Platoâs attempt to propose a new type of physics that addressed the shortcomings of Presocratic enquiries into nature, which purported to explain phenomena without reference to the soul.
-
The critique of Platonic physics formed part of a broader reflection on the principles and their connection with sensible phenomena. The study of these principles did not necessarily take the form of a theology or an attempt to arrive at knowledge of divine beings, but rather presented itself as the essential stage in a new type of theoria.
The Assos period thus emerges as a time of intellectual flourishing, in which the evolution of Peripatetic thought was shaped more by common lines of investigation than by direct opposition to Academic doctrines. Although it is still uncertain whether Theophrastus was actually present at Assos, recent scholarship has reassessed his Metaphysics in a way that is entirely consistent with the intellectual climate of Assos, sometimes even explicitly mentioning Assos.12 Rather than viewing Theophrastusâ Metaphysics as a post-Aristotelian work or merely a critique of Book
That said, to what extent can this perspective be extended to the study of Theophrastusâ De igne? A pivotal development in addressing this question has been the reassessment of De igneâs supposedly anti-Aristotelian outlook. The traditional interpretation, established by scholars such as Eduard Zeller, emphasised the fundamental compatibility between Theophrastusâ and Aristotleâs physical theories, with Zeller highlighting their shared views about the nature of fire.15 This claim received support from Otto Regenbogen in his Pauly-Wissowa entry, in which he argued that the originality of De igne did not lie in its theses, many of which could be traced back to Aristotle. This interpretation was famously challenged by Peter Steinmetz, whose 1964 monograph emphasised the independence and originality of Theophrastusâ physics. Steinmetz argued that the divergence from Aristotelian doctrine was, in reality, more significant, crediting Theophrastus with a methodological shift and pointing to a decisive break with core Aristotelian principlesâmost notably, through what he interprets as a rejection of the fifth element and a turn toward atomistic theory.16 More recent scholarship has, however, reassessed the extent of this divergence, concluding that, despite its critical stance, De igne remains deeply embedded in Aristotelian thought, and potentially even in its treatment of aether.17
My own view is that rather than reflecting a turning away from enquiries into first principles on the part of Theophrastus, De igne was deeply shaped by the methods and research traditions of the Academy. In the absence of new historical evidence, this paper does not focus on whether Theophrastus was actually present at Assos, but instead examines the extent to which De igne reflects the intellectual framework of Assos. This is not a matter of merely historical interest, since it offers new insights into the methods and dynamics of the early Peripatetic school and its complex relationship with the Academy.18 The specific claim I make here is that De igne bears the imprint of three distinct influences: (1) Platoâs Timaeus;19 (2) Aristotleâs critique of Platoâs account of fire and heat, in which he sought to address its alleged explanatory limitations and internal contradictions; and (3) the challenges that emerged from Aristotleâs own attempts to resolve these issues, particularly when it came to reconciling the properties of fire with a coherent and well-founded theory of the elements. On this hypothesis, De igne is informed by the philosophical problems connected to the nature and priority of the elements within a closed system that is not sustained by transcendent principles rather than by Theophrastusâ supposed lack of interest in higher principles. The question is: if an element is considered ontologically prior, how can it simultaneously possess different qualities? Theophrastusâ original solution to this problem opens up a new perspective on the difficulties Aristotle faced in conceptualising the relationship between heat and fire, as well as in articulating the different definitions of fire. While it is bold to suggest that, because Theophrastusâ solution avoids some of the problems faced by Aristotle, his characterisation of fire was intended specifically to circumvent them, many methodological questions are explicitly raised by Theophrastus himself.
In order to bring out the coherence of De igneâa work frequently considered an unstructured compilation of notes20âI will begin by reconstructing its Academic and Aristotelian background. I will then examine how Theophrastusâ characterisation of fire navigates challenges arising in both traditions. Finally, I will argue that although Theophrastusâ account successfully explains phenomena such as heat, it does so at the expense of considerations about the nature of the elements. I will thus provide a new perspective on Theophrastusâ apparent reluctance to conduct a comprehensive enquiry into the first principles and reframe his focus on fiery phenomena, arguing that it is not a manifestation of his interest in trivial observations, but the outcome of a deeper reflection on physical theory. I suggest that De igne reflects Theophrastusâ recognition of an implicit tension between explaining observable phenomena and establishing the coherence of a self-contained physical system, arguing that his work prioritises the formerâa methodological choice that sets him apart from Aristotle.
1 The Enquiry into First Principles and Theophrastusâ Study of Fire
Gaiserâs hypothesis that Theophrastus was part of the Assos circle rested on two heterogeneous arguments. The first was a novel interpretation of §â¯46 of Theophrastusâ De igne, particularly the phrase
Although the treatise appears to assume the existence of simple bodies, this premise seems to be more of a commonly accepted idea than a demonstrated thesis. From the outset, then, we are confronted with an important ambiguity regarding the status and scope of De igne: does the enquiry start from the first principles and move towards the study of fire, or does it proceed from the study of fire towards the first principles? If we accept the latter hypothesis, the investigation of first principles would serve merely as the background against which the main argument takes shape. By contrast, the former hypothesisânamely that the study of fire is undertaken within the context of a broader enquiry into the first principles of natureâappears more consistent with the research conducted in Assos. Moreover, this reading is supported by the phrasing and rhythm of the opening sentence, which underscores the singularity of fire among the so-called âsimple bodiesâ. The discussion of simple bodies fits naturally within an Academic research programme, as outlined in the Protrepticus, which established a direct relationship of dependence between knowledge of the whole and knowledge of the first principles:
For whether it is fire or air or number or any other natures that are the causes and principles of other things, if we are ignorant of them we cannot know any of the other things; for how could one recognise speech if one did not know the syllables, or know these if one knew none of the letters (
μηδὲν Ïῶν ÏÏοιÏείÏν )?27
In this passage, fire is mentioned as a possible first principle alongside other natural bodies, such as air. While the focus on physical bodies might suggest an Ionian perspective that seeks to identify which physical body underlies all things, the inclusion of number as a potential first principle reveals the Academic framework of the text. This debate about first principles is echoed in Platoâs Timaeus:
We must, in fact, consider in itself the nature of fire and water, air and earth, before the generation of the Heaven, and their condition before the Heaven was. For to this day no one has explained their generation, but we speak as if men knew what fire and each of the others is, positing them as original principles, elements (as it were, letters) of the universe; whereas one who has ever so little intelligence should not rank them in this analogy even so low as syllables.28
The parallel with the Protrepticus is striking: both texts implicitly compare hierarchically arranged principles to letters and syllables, and they both consider fire as a possible primary explanatory principle. However, the Timaeus goes on to reject this idea, suggesting that fire cannot serve as a first principle, as it is not even comparable to a syllable, let alone a letter. The implied reason for this is its inherent obscurity, as indicated by the remark: âas if men knew what fire and each of the others isâ, echoing Timaeus 49B (âit is hard to say, with respect to any one of these, which we ought to call really water rather than fireâ).29 While the Timaeus explicitly dismisses the notion that fire could be a first principle, this discussion suggests that the hypothesis was debated, indicating that Theophrastusâ emphasis on the specificity of fire in De igne extends beyond a mere Heraclitean reference. Furthermore, the Timaeus conducts its enquiry into the first principles within a generative framework that emphasises the question of the origin of the elements and the broader issue of how all things could emerge from them.
Theophrastusâ Metaphysics testifies to both his interest in enquiries into first principles and his engagement with the Timaeus:
Perhaps one might raise the aporia, how and of what sort one should at all suppose the first principles to be: whether shapeless and, as it were, potent (as do those who posit fire and earth), or already shaped, on the ground that it is necessary most of all for these to be determined, as he says in the Timaeus.30
Here, Theophrastus contrasts two possible approaches to defining first principles: we can do so either through shapes, as in the Timaeusâwhere triangles serve as the fundamental constituents of the elementsâor through powers (
For the heat and the power of heat are a principle. For heat is more common, reaches further, and exerts more influence on qualitative change and natural generation, whereas fire, as has been said, is productive of itself, but destructive of other things in most cases. From this it will also be clear that the nature of fire is different from the nature of heat.32
As a general rule, Theophrastusâ account of fire for the most part echoes Aristotelian theses. For example, as already highlighted by Eduard Zeller,33 §â¯26 of De igne states that âfire is hot and dryâ, directly paralleling Aristotleâs definition of fire in De generatione et corruptione II 3, 330b3. Moreover, in the opening lines of De igne, Theophrastus connects his description of fire as a self-generating body to Aristotleâs thesis that a smaller fire is consumed by a larger one:
Fire, however, is of such a nature as to generate and destroy itself, the lesser fire to generate the greater, and the greater fire to destroy the lesser.34
While the thesis that the smaller fire generates the larger one directly follows from Theophrastusâ definition of fire as a burning process, the second part of the sentence, which states that a smaller fire is destroyed by a larger fire, reflects a core Aristotelian principle. Not only is this thesis consistently repeated and sometimes attributed to earlier thinkers,35 but it also plays a crucial role in Aristotleâs theory of the preservation of life, particularly in relation to the need for a cooling principle.36 Although Theophrastus largely upholds Aristotelian theses from the outset of De igne, the way in which he frames his enquiry reflects his originality as a thinker, a point noted by Regenbogen, who examined the specific ways in which these questions are posed and interconnected.37 In addition to assessing the primacy of heat or fire as a first principle, the opening of De igne raises the question of how fire can be considered a first principle if it always requires fuel. Theophrastus also explores the relationship of fire to the heat of the sun and the warmth found in living beings, an issue likewise addressed by Aristotle:
This is not fire nor any such force, but it is the breath included in the semen and the foam-like, and the natural principle in the breath, being analogous to the element of the stars. Hence, whereas fire generates no animal and we do not find any living thing forming in either solids or liquids under the influence of fire, the heat of the sun and that of animals does generate them. Not only is this true of the heat that works through the semen, but whatever other residue of the animal nature there may be, this also has still a vital principle in it. From such considerations it is clear that the heat in animals neither is fire nor derives its origin from fire.38
However, De igne does not clearly establish a connection between fire and heat, or between fire and the sunâit raises these issues without offering a definitive resolution.39 Consequently, even if one acknowledges that a shared enquiry into the physical first principles within the Academy formed part of the intellectual backdrop, Theophrastus deliberately distances himself from this line of questioning from the outset. While the frequent references to first causes in De igne suggest that such an enquiry is acknowledged as a possible avenue of research, the treatise itself remains primarily concerned with the empirical manifestations of fireâa topic that Theophrastus explicitly differentiates from âan inquiry into first causesâ:
But this seems to lead us off (
á¼ÎºÏá½³Ïειν ) into an inquiry of greater scope than the present one, an inquiry into first causes.40
Thus, while Theophrastus acknowledges the relevance of studying the first causes, he consistently sets this pursuit aside, considering it to lie beyond the scope of his enquiry.41 Nonetheless, I argue that the Academyâs approach to first causes is not simply dismissed in §â¯7, but continues to shape De igne throughout, particularly in Theophrastusâ characterisation of fire as a self-generating body. While this characterisation does not establish fire as a primary principleâalthough it is notable that no other simple body holds a stronger claimâit adeptly navigates the challenges posed by both Platoâs and Aristotleâs accounts of elemental fire.
2 Theophrastusâ Original Characterisation of Fire and Its Philosophical Stakes
The aim of this section is to highlight the Platonic and Aristotelian background of Theophrastusâ characterisation of fire, in order to shed light on its philosophical stakes. This Academic background is reflected not only in the theses that are defended in De igne, but also in the specific aporiai it seems to address. For example, Gaiser traces the three forms of fire that appear in De igneâflame (
Next we must observe that there are several varieties of fire: flame; that effluence from flame which does not burn but gives light to the eyes; and what is left of fire in glowing embers when flame is quenched.43
Likely drawing on the same tradition, Aristotle also refers to light, flame and charcoal as three species of fire in Topics VÂ 5.44 While continuing to acknowledge this tripartition, Theophrastus notably invokes it to underline the need for a substrate:
Fire is in a substrateâwhich in any case is clear to our perception of the world around us, whether light should or should not be reckoned to be included in it. For if light also [should be considered as a kind of fire], it is obvious that this exists in air and water in any case; if not, the fire of flame and of charcoal in any case are in a substrate.45
Fire is thus described as a dynamic process, characterised by its unique ability to generate itselfâa
The nature of fire has the most peculiar powers among the simple bodies. For air, water, and earth perform their natural changes only into one another, while none is itself generative of itself; fire, however, is of such a nature as to generate and destroy itself, the lesser fire to generate the greater, and the greater fire to destroy the lesser.46
Theophrastusâ description notably avoids the two alternatives outlined in his Metaphysics (6b23â27, see supra): i.e. defining a first principle either by (i) assigning it a specific geometric shape, as in the Timaeus, or by (ii) attributing to it a distinctive power, such as the capacity to heat, a move that can lead to conceiving it as an excess of heat (
In short, everything that is burning is, in a sense, in generation, comparable with motion, for which reason it somehow is destroyed as it is created, and with the exhaustion of the fuel, it itself is done away with. The ancients were referring to this when they said that fire always seeks nourishment, being unable to persist without fuel. Hence it seems foolish to speak of fire as a first substance and original element if it cannot exist without fuel. For in that case it is not elemental nor prior to the substrate and the fuel, unless there is some such substance in the first heavenly sphere itself which is pure, unmixed heat. In that case it would no longer burn. But burning is the essence of fire, unless indeed there are several different kinds of fire, one pure and unmixed, an element, the other located in the earthâs sphere, mixed, and always in generation.48
The emphasis on generation in Theophrastusâ text is noteworthy. As mentioned above (p. 46) in connection with the Timaeus, Academic enquiries into first principles adopted a generative framework. Similarly, in De caelo III 1, which I have argued has a substantial Academic background,49 Aristotle explicitly connects the enquiry into simple bodies with the study of generation. Theophrastus takes a different approach, however, defining fire through its capacity to burnâa process that is intrinsically tied to generation. Burning is not conceived of as a heating process, but as an act of transformation (i.e. turning fuel into fire). Fireâs ability to burn is presented as its essential nature: âIn that case, it would no longer burn. But burning is the essence of fireâ (
The thesis that fire is able to generate itself was originally advanced by Aristotle, for example in the Parva naturalia:
But in other cases the result is exhaustionâwhen the heat accumulates excessively owing to lack of respiration and of refrigeration. For the heat, accumulating in great quantity, quickly uses up its nutriment and consumes it all before more is sent up by exhalation. Hence not only is a smaller fire readily put out by a larger one, but of itself the lampâs flame is consumed when inserted in a large blaze, just as is the case with any other combustible. The reason is that the nutriment in the flame is seized by the larger one before fresh fuel can be added, for fire is ever coming into being and flowing like a river, but so speedily as to elude observation. Clearly, therefore, if the bodily heat must be conserved (as is necessary if life is to continue), there must be some way of cooling the heat resident in the source of warmth.50
In this passage, the ability of fire to continuously generate itself, as long as fuel is available, is compared to the flow of a river, a likely allusion to Heraclitus. However, this characteristic of fire is mentioned in other Aristotelian contexts, which shows that it is integrated into Aristotleâs account of fire.51 Finally, Theophrastusâ characterisation of fire seems to take into account an objection raised by Aristotle to Platoâs attribution of a pyramidal shape to fire (and Democritusâ attribution of a spherical one):
Again, combustion of a body produces fire, and fire is a sphere or a pyramid. The body, then, is turned into spheres or pyramids. Let us grant that these figures may reasonably be supposed to cut and break up bodies; still it remains quite inexplicable that a pyramid must needs produce pyramids or a sphere spheres. One might as well postulate that a knife or a saw divides things into knives or saws.52
In this passage, Aristotle once again associates combustion with fire, as his objection is fundamentally based on the combustion process. He rejects the notion that the nature of fire is determined by geometric shapes, arguing that while fire generates more fire through combustion, solids do not produce more solids. By emphasising the centrality of the combustion process without assigning fire a specific geometric form, Theophrastus seems to acknowledge and incorporate this Aristotelian critique. It is noteworthy that, in the Aristotelian texts, the ability of fire to generate itself is presented as a mere property of fire and not its essence. Theophrastusâ innovation thus lies not in introducing a new thesis about fire, but in shifting the emphasisâmaking self-generation the main characteristic of fire.
My claim here is that this new characterisation allows Theophrastus to circumvent the challenges Aristotle faces in defining fire, which arise from his not relying, as Plato does, on an extrinsic principle, such as a geometric figure. This approach exemplifies a philosophical pattern that may be characteristic of Theophrastusâ works in Assos, at least as it has been reconstructed by Jaeger and Gaiser: criticising Plato from a Peripatetic perspective, while skilfully avoiding the difficulties Aristotle encountered in reforming Academic theories. In this specific case, Aristotleâs rejection of the geometric determination of primary bodies forces him to develop an alternative framework to account for the definitional properties of elemental bodies. However, the abandonment of extrinsic principles when defining a simple body gives rise to at least two significant challenges within Aristotleâs account:
-
Articulating the relationship between fireâs various proper predicates and its essence. Connecting what is merely proper to fire with what constitutes its essential definition poses a genuine difficulty for Aristotle. Moreover, this difficulty highlights the paradoxical notion of primacy, as an element is supposed to be a prior concept and therefore should not rely on a principle of articulation to conciliate heterogeneous properties. A related issue pertains to the determination of fireâs essence, as opposed to its proper predicates. This includes questions such as whether fire is defined by its motionâspecifically, its natural upward movementâor by its essential primary qualities, such as dryness and heat.53
-
Drawing a distinction between truly elemental fire and other forms of fire. Establishing the nature of the relationship between elemental fire, as defined in its pure, theoretical form, and empirical fire proves challenging, regardless of its various manifestations in sensory experience.
These two issues come to the fore in following passage from De generatione et corruptione:
In fact, however, fire and air, and each of the bodies we have mentioned, are not simple, but combined. The simple bodies are indeed similar in nature to them, but not identical with them. Thus the simple body corresponding to fire is fire-like, not fire; that which corresponds to air is air-like; and so on with the rest of them. But fire is an excess of heat, just as ice is an excess of cold.54
In merely suggesting a resemblance between simple (pure) bodies and composite bodies (i.e. those commonly encountered), Aristotle remains ambiguous. The relationship between familiar elements, such as fire or earth, and their pure forms remains unclear. How do simple bodies manifest within the mixed bodies we perceive? If terrestrial fire shares the form of pure fire, is the difference between them solely due to the fact that the former is mixed with other elements? If so, what role does the substance with which it is mixed play in determining the form of the composite body? As a result, the connection between first principles and terrestrial bodies remains elusive within Aristotleâs account.
The contrast between pure fire and another form of fire that is almost fire is displayed in another Aristotelian text, Meteorology IÂ 3, albeit in a somewhat different form. Here, the distinction is no longer between empirical fire and pure, elemental fire, but between two kinds of fire that are not commonly encountered in everyday experience:
From another point of view we may look [at the motion] as follows. The body that lies below the circular motion of the heavens is, in a way, matter, and is potentially hot, cold, dry, moist, and possessed of whatever other qualities are derived from these. But it actually acquires or retains one of these in virtue of motion or rest, the cause and principle of which has already been explained. So at the centre and round it we get earth and water, the heaviest and coldest elements, by themselves; round them and contiguous with them, air and what we commonly call fire. It is not really fire, for fire is an excess of heat and a sort of ebullition.55
In this passage, Aristotle contrasts true fireâdefined, as in De generatione et corruptione, as an âexcess of heatâ (
Aristotle diverges here from Theophrastusâ approach by attributing the excessive heat of this âfireâ to the influence of the aether. The only connection between true fire and the
The difficulty facing Aristotle illustrates the architectonic challenge of establishing a criterion for identifying an element as such and reveals the antinomic tensions inherent in the notion of elements. For example, fire exists both within the physical system, as empirical fire involved in transformations, and at its boundaries, serving to close causal explanations and mark out the limits of the physical system. This raises the question of how we can reconcile the different types of fire and their distinct functions as outlined by Aristotle. Moreover, what principle makes it possible to articulate Aristotleâs various definitions of fire? Within the framework of De caelo, natural motion defines the nature of bodies. It seems that motion functions as the explicans rather than the explicandum: it constitutes the form of the elemental body, as suggested in De caelo IVÂ 3.58 That said, how can we reconcile fireâs lightness with its heat without resorting to an arbitrary or forced connection? This difficulty appears to have been recognised by Aristotle himself, as indicated in the following passage from Parts of Animals:
Now there are three degrees of composition; and of these the first in order, as all will allow, is composition out of what some call the elements, such as earth, air, water, fire. Perhaps, however, it would be more accurate to say composition out of the elementary forces; nor indeed out of all of these, as said elsewhere in previous treatises. For wet and dry, hot and cold, form the material of all composite bodies; and all other differences are secondary to these, such differences, that is, as heaviness or lightness, density or rarity, roughness or smoothness, and any other such properties of bodies as there may be.59
Although Aristotle claims that lightness and heaviness can be derived from moisture, dryness, heat and cold, he does not spell out the details of this derivation. This omission underscores a real challenge in the articulation of his framework, as he merely juxtaposes lightness and heaviness with heat and dryness in the case of fire, without providing a clear explanation of their interrelation. Within the Aristotelian corpus itself, we thus encounter several definitions of fire that do not seem to refer to the same entity.60
Conversely, Theophrastus minimises the gap between phenomenal fire and elemental fire,61 thereby sidestepping the challenge of explicitly connecting them. Moreover, by rejecting a definition of fire based on a single quality, such as upward motion or heat, Theophrastus offers a seemingly clearer, albeit initially paradoxical, solution. Nonetheless, he does not abandon the qualities traditionally ascribed to fire in the Peripatetic traditionâsuch as heat62ânor does he abandon the notion of natural motion, as is evident in his critique of Democritusâ account of flame:
But the view of those who speak of the motion of the air which encounters the flame is quite ridiculous. The fire is self-moving and it imparts motion to the air rather than receives it from the impulse of the air, since when the weather is calm, the pointed shape of the flame is no less in evidence.63
This passage should not be interpreted as a departure from the standard Aristotelian thesis that fire possesses an upward motion. Theophrastus is not asserting that fire is genuinely self-moving, which would contradict Aristotleâs careful efforts in De caelo IV and Physics VIIIÂ 4 to avoid such a claim. Rather, his argument targets the view that fireâs upward motion is merely accidental, resulting from its being pushed by air. Theophrastus instead suggests that fire is moved by fire itself, in the sense that it grows and propagates. Ultimately, while heat and natural motion remain closely associated with fire in Theophrastusâ account, neither is presented as its defining essence. It is precisely this distinction between essence and observable qualities that enables Theophrastus to articulate a coherent explanation of these characteristics, as the final section of this paper will demonstrate.
3 Explaining Phenomena vs. Establishing Priority: A Theophrastean Dilemma?
Although heat is consistently associated with fire in Theophrastusâ De igne,64 the precise relationship between them remains elusive. In order to clarify this connection, it would be necessary to resolve the problem posed in §â¯5, namely to establish the nature of the link between the sun (potentially conceived as elemental fire) and empirical fire, understood as a burning process.65 Simply identifying the sun as a form of fire would be insufficient, as it would still be necessary to reconcile celestial, non-burning fire with empirical, combustible fire under a single concept. This problem remains unsolved, as evidenced by the ongoing scholarly debate on whether De igne endorses Aristotleâs notion of aether (see supra). Nevertheless, Theophrastusâ account of fire offers a satisfactory and systematic explanation of heat, effectively addressing some of the major difficulties faced by both the Aristotelian and the Platonic accounts. My aim in this section is to demonstrate that Theophrastusâ emphasis on explaining fiery phenomena and heat does not merely reflect an empirical focus, but rather a methodological engagement with the fundamental tension between fireâs role as an element within a physical system and its observable effect, namely heat production. To that end, I will begin by examining the methodological criticism made by the Peripatetics of Platoâs explanation of heat in the Timaeus, before examining the challenges arising from Aristotleâs attempts to link heat and his definition of elemental fire. Against this background, I will argue that Theophrastusâ decision to leave the elemental status of fire unresolved enables him to develop a coherent account of heat, one that strategically draws on Platonic insights while avoiding the difficulties inherent in Aristotleâs approach.
At first glance, Platoâs account of fire successfully reconciles its determination as tetrahedron with its primary quality: the production of heat. Of the regular solids, the tetrahedron possesses the sharpest angles and the fewest faces, making it the most suitable candidate for fire:
Accordingly we shall preserve the probability of our account, if we assign this figure to earth; and of the remainder the least mobile to water, the most mobile to fire, and the intermediate figure to air. Again, we shall assign the smallest body to fire, the largest to water, and the intermediate to air; and again the body with the sharpest angles to fire, the next to air, the third to water. Now, taking all these figures, the one with the fewest faces (pyramid) must be the most mobile, since it has the sharpest cutting edges and the sharpest points in every direction, and moreover the lightest, as being composed of the smallest number of similar parts.66
Aristotle criticises this theory by presenting a general criterion for assessing the validity of a physical theory. A robust theory must be both coherent and comprehensive, offering explanations that extend beyond isolated phenomena. It should not offer ad hoc justificationsâe.g. accounting for heat while failing to explain coldâbut instead present a unified framework capable of addressing the full range of natural phenomena:
In addition, since hot and cold are contrary powers, it is impossible to allot any shape to the cold. For the shape given must be the contrary of that given to the hot, but there is no contrariety between figures. That is why they have all left the cold out, though properly either all or none should have their distinguishing figures.67
Aristotleâs point is not that Plato fails to provide a theory of cold; such a theory is explicitly presented in Timaeus 62a. Rather, he takes aim at the inconsistency of Platoâs account of heat and cold, and more generally the use of shapes to determine simple bodies and physical powers. According to Aristotle, shapes cannot account for physical powers, as long as such powers possess contraries.68 To justify his claim, Aristotle invokes an irreconcilable contrast between shapes and physical powers. Physical powers inherently involve opposition, as the same matter can be affected in opposite waysâe.g. being either warmed or cooled. However, no shape can stand in opposition to another in the same way. Therefore, no shape can adequately explain a physical power. Remarkably, a passage from Theophrastusâ De sensibus closely echoes Aristotleâs criticism:
Yet this is also absurd. First of all, he gives no uniform account of all things, not even of those that belong to the same class. For he describes heat in terms of figure, but he has not given a like account of cold.69
Theophrastus similarly attacks the lack of coherence in Platoâs attribution of regular solids to simple bodies, pointing out that âno uniform account of all thingsâ is provided. However, the strength of Platoâs approach lies in its ability to unify the determination of fire with the production of heat. In contrast, Aristotleâs account of heat struggles to establish a clear connection between heat as an observable phenomenon and its role as a defining characteristic of fire:
In some of the bodies which are called hot the heat is derived from without, while in others it belongs to the bodies themselves; and it makes a most important difference whether the heat has the former or the latter origin. For one of them comes close to being hot accidentally and not in its own rightâas if, finding that some man in a fever was a musician, one were to say that musicians are hotter than healthy men. Of that which is hot per se and that which is hot per accidens, the former is the slower to cool, while not rarely the latter is the hotter to the touch. The former again is the more burning of the twoâflame, for instance, as compared with boiling waterâwhile the latter, as the boiling water, which is hot per accidens, is the more heating to the touch. From all this it is clear that it is no simple matter to decide which of two bodies is the hotter. For the first may be the hotter in one sense, the second the hotter in another. Indeed in some of these cases it is impossible to say simply even whether a thing is hot or not. For the actual substratum may not itself be hot, but may be hot when coupled with heat as an attribute, as would be the case if one attached a single name to hot water or hot iron. It is after this manner that blood is hot.70
This passage attempts to draw a distinction between heat by nature and heat by accident, contrasting a flame, which is inherently hot, with boiling water. Although this distinction arises in a biological context and aims to explain how blood is hot, it can be situated within a broader framework, namely Aristotleâs attempt to connect heat to the elemental nature and defining principle of fire. However, this approach raises at least two significant challenges. The first challenge is that the distinction in question does not have a clear experiential basis, a difficulty that is acknowledged by Aristotle (âfrom all this it is clear that it is no simple matter to decide which of two bodies is the hotterâ). Perception, for example, does not allow us to determine whether something is hot by nature or by accident, as boiling water âis the more heating to the touchâ. The second challenge is the lack of an explanation for why something that is hot by nature should retain its heat longer than something that is hot by accident, highlighting the absence of a comprehensive theory of heat. In contrast, Theophrastusâ theory of heat provides a consistent and systematic framework that accounts for a wide range of phenomena:
Thus we may lay all these and like phenomena to the fineness or the coarseness of the fuel. For example, the flame from reeds heats flesh and reeds are light, compact because they are continuous. A fire that is fine can penetrate, and the heat is made possible by the continuous admixture of the fuel. The flame of reeds then is in generable preferable to the heat of charcoal; its output is both greater and more concentrated.71
In Theophrastusâ theory, much like in the Timaeus, the production of heat is consistently explained as a phenomenon of penetration (
Now the heat which is natural to animate bodies, being infused into a comparatively large number of creatures and in a rather special way becomes in a sense alive and capable of generating similar creatures. Even more so the heat from the sun. It is able to create animals and plants. It is mixed, to be sure with air (occurring rather in it),72 but by reason of its gentleness and fineness has a certain appropriateness for generating life; it is not, like the heat of fire, hard and caustic.73
In a manner reminiscent of Aristotleâs mention of proper heat (
In a similar vein, Theophrastus is able to consistently account for the upward motion of fire:
If fire moves in a kind of rush or flow, and the result for all flowing things is that they diminish over time unless replenished from another source, then it is necessary that, as it extends into a larger space, it becomes narrower while maintaining continuity. Thus, this could also explain the shape of the flame: the base is the strongest and most abundant, and from there it diminishes continuously, weakening as it ascends, though it preserves its continuity.75
This passage explains not only the shape of the flame, but also its motion. As fire âextends into a larger spaceâ, it does not remain confined to its place, but its behaviour resembles a continuous flow. This echoes the description of fire quoted above in Aristotleâs De juventute et senectute. However, within Theophrastusâ framework, the upward motion of fire is not conceived of as a movement of actualisation toward its form, nor does it play a role in defining fire as an element, as it does in Aristotleâs account in De caelo IV. Instead, Theophrastusâ explanation aligns with his characterisation of fire as self-generating: fire originates from its core and diminishes as it moves away from its fuel source.
The comparison with Aristotleâs approach to heat and upward motion suggests that Theophrastusâ ability to articulate a consistent account of fiery phenomena stems precisely from his decision not to fully engage with the elemental status of fire. Instead, he adopts a distinctly analytical approach, explaining the heat and upward motion of fire in terms of combustion, which he treats as the primary factor responsible for both. By refraining from making heat the defining characteristic of fire or establishing fire as the fundamental principle of heat, Theophrastus develops a coherent explanatory framework that extends beyond fire to encompass other forms of heat.
However, the precise role of combustion in the definition of fire remains ambiguous, beyond being described as one of its âmost peculiar powersâ (§â¯1,
4 Conclusion
This paper has sought to challenge the view that Theophrastusâ De igne is the work of a resigned empiricist who had abandoned the study of principles, while also rejecting the comparison that has occasionally been made of Theophrastus to a modern scientist constructing a physical theory through systematic observation and experimentation. Instead, De igne reveals itself as a work that is shaped on a deep level by the philosophical dialogue between the Platonic and Aristotelian traditions, particularly with regard to the challenges posed by the enquiry into the elements. While Theophrastus appears to set this issue aside at the outset, it remains a persistent undercurrent throughout the treatise, informing his approach to fire and heat. The aporetic method evident in De igne offers a productive way to apply the genealogical approach and assess its heuristic value in a novel manner. Since Theophrastus does not elaborate a dogmatic theory and, as has been noted, none of his core claims about fire are entirely new but were already upheld by Aristotle, the Assos reference does not help trace the evolution of specific theses. Rather, it highlights a shared set of questions and problems directly connected to the Academy. The effect is to recast Theophrastus not as a reader of Aristotle, commenting on an established corpus, but rather as a colleague independently drawing on the same Academic tradition to address the same challenges, such as the tension between providing a limited but consistent explanation of observable phenomena and engaging with the paradoxes bearing on the nature of the elements. In this regard, De igne appears not so much âpost-Aristotelianâ, as it is sometimes labelled (e.g. in the subtitle of Coutantâs edition), but rather as para-Aristotelian.77
The most systematic presentation of this view is found in Rapp (2019). In Boureau (Forthcoming), I argue that while this method has sometimes been applied in an insufficiently rigorous way, genealogical approaches can be employed with greater nuance and need not be incompatible with a systematic interpretation of Aristotleâs philosophical thought.
Theophrastus, De igne, §â¯45.
I am quoting here from Robinsonâs 1948 English translation of this book, which was revised and expanded by the author.
This interpretation is spelled out in Battegazzore (1984), 48: âLa caratteristica saliente del De igne risulta essere lâassorbimento di ogni traccia metafisica in un sistema esclusivamente fisico e concreto: i quattro tradizionali elementi non sono più considerati i principi ultimi e teorici della realtà , ma corpi (
Jaeger (1948), 124.
Jaeger (1948), 128 and 172.
See Jaeger (1948), 306 n. 1: âWe must therefore suppose that the work On the Heaven mainly arose, or that the first draft of it was sketched out, during his middle period, and that revisions, some of them drastic, took place during his later years.â See also Jaeger (1948), 306: âIt was written after the dialogue On Philosophy, and therefore at the earliest one or two years after Platoâs death. It was probably not much later than this, however, for the whole point of view is that of the later Academy.â
Jaeger (1948), 124.
See Jaeger (1948), 124â125: âAt the same time, everything points to the conclusion that his close affinity with Plato and Platoâs preoccupations continued undisturbed. He went on living and teaching among Platoâs pupils. As we have seen, his departure from the school at Athens was in no sense a break with the Academic community as such [â¦]. We discover that between the early, dogmatically Platonic, stage of his development, and the final form of his thought in its maturity, there was a period of transition whose nature can be definitely ascertained in many particulars, a period when he was criticizing, rearranging, and detaching himself, a period, previously wholly overlooked, which was clearly distinct from the final form of his philosophy, although it reveals the entelechy of the latter in all essential points.â
Jaeger (1948), 172: âThus the original form of the criticism presupposes a group of Platonic philosophers, for whom Aristotle once more sums up, in a rapid survey, all those objections to the doctrine of the now dead master that had occupied the Academy in the course of the years, in order to infer the necessity for a complete reorganization of Platonism on the basis of these criticisms.â See also Jaeger (1948), 173, for the composition of this group, which included âPlatoâs best-known disciples, men who were either objective enough to listen to an opponentâs reasons, like Xenocrates, or themselves full of doubt about Platoâs doctrine, as Erastus, Coriscus, and their convert Hermias, seem to have been.â
While Jaeger (1948), 303, acknowledges that the enquiry into the eternity of the world in the first book of De caelo and Aristotleâs De philosophia constitutes âa running polemic against Platoâs Timaeus, which is explicitly mentionedâ, he places greater emphasis on the internal discussions within the Academy concerning physical matters than on direct engagement with the Timaeus itself. Jaeger (1948), 300: ânevertheless, the disposition of the books On the Heaven does at any rate enable us to observe how Aristotleâs cosmology arose out of Platoâs. We know the latter directly only from the Timaeus, behind which lie the far-reaching Pythagorean speculations of the school, and it is therefore very important that this work of Aristotleâs allows us a glimpse of the discussions that went on about the subject in the Academy.â However, it seems to me that the discussion of the treatise was more influential than Jaeger suggests.
See Gutas (2010), 8: âThese considerations make it certainly possible, and very much probable, that the Essay may have been written in Assos, giving us 347 as the earliest date of composition. Accordingly, it can be maintained with as much certainty as is possible in such cases that Theophrastusâs On First Principles was written in the period between 347 and 334.â
See, e.g., Gutas (2010), 31: âFurthermore, if one keeps the date of composition of the Essay in mind, and that it was written at the time when Aristotle himself was grappling with the problems discussed in it and had composed book Lambda, definitely, and possibly also Alpha Meizon and Beta on the very subject, it becomes apparent how naturally Theophrastusâs Essay fits in their context and continues the discussion initiated in them.â
Lefebvre (2015), 37â38: âThéophraste avait manifestement une problématique propre sur la question des principes; son orientation générale est différente de celle dâAristote, même si elle utilise en partie une même matière.â
Zeller (1963) II/1, 832â833: âIn der Lehre von den Elementen, welcher die uns erhaltene Abhandlung über das Feuer angehört, hielt Theophrast zwar die aristotelische Grundlage fest, aber doch fand er auch hier Schwierigkeiten.â
Steinmetzâs arguments did not, however, result in a lasting consensus. For example, in his 1967 review, Hans Gottschalk underscored the inadequacy of the evidence supporting Steinmetzâs claims. In contrast, James Longrigg found that Steinmetz âargue[d] persuasivelyâ with regard to the differences between Aristotleâs and Theophrastusâ conceptions of fire and elemental bodies (Longrigg 1966, 179).
The issue remains a matter of ongoing debate. For instance, Marlein van Raalte (2010), 48, argues that it is âvery unlikelyâ that âTheophrastus adhered to the Aristotelian concept of aetherâ. However, as István Bodnár (2002b), 76, points out, even if we grant that Theophrastus considered the matter of the heavens to be âfireâ, it would be âfire in an etiolated sense onlyâ, merely âa more mundane variant of the Aristotelian aetherâ. Similarly, David Lefebvre (2017), 61 notes that Aristotle himself may at some point have accepted that the heavens were filled with a kind of âfireâ possessing properties distinct from ordinary fire. He also contends (Lefebvre 2017, 76) that there is no major doctrinal divergence between Theophrastus and Aristotle concerning the nature of fire.
Jaeger (1948), 172: âThe bereaved school is now standing at a decisive turning-point of its career. Outside of Athens, which he very soon left, Aristotle was surrounded by such a group of Platonists, after Platoâs death, only in Assos, and then never again.â
On Theophrastusâ acquaintance with the Timaeus, see the hypothesis advanced by Han Baltussen (2000), 131â132, to the effect that Theophrastusâ remarks in the De sensibus are based not on the full text but partly on a summary. See also Baltussen (2003), 56, which introduces a further assumption that Theophrastus âused a summary version as a working manuscript for personal use only alongside the âcompleteâ Timaeus textâ.
See, e.g., Coutant (1971), IX: âIt seems probable that the work is a collection of lecture notes rather than an organized presentation in the sense that the works on botany are. First and foremost, the work does not have any central idea pervading it but is rather a medley of sub-topics occurring disjointedly and with an occasional reprise.â See also Battegazzore (1984), 46: âVa peraltro subito precisato che il De igne, quale a noi è pervenuto, non è una trattazione organica, e non aspira a nessuna completezza, ma è viziato da unâintrinseca desultorietà : il fatto stesso che i riferimenti e le allusioni alle teorie di precedenti filosofi siano sporadici e sfumati.â
Gaiser (1985), 28â35.
Gaiser (1985), 32â35.
See, e.g., Engberg-Pederson (1987).
Gaiser (1985), 41.
Theophrastus, De igne §â¯7, 3â4:
Theophrastus, De igne §â¯1, 1, transl. Van Raalte:
Aristotle, Protrepticus (Iamblichus, Protrepticus VI, 39, 15â19 = Fr. 52 Rose = Fr. 5 Ross, Walter = Fr. 36 Düring), transl. Barnes & Lawrence:
Plato, Timaeus 48bâc, transl. Cornford:
Plato, Timaeus 49b, transl. Cornford:
Theophrastus, Metaphysics 14, 6b23â27, transl. Gutas:
Aristotle, De caelo IVÂ 3, 310a31âb1, transl. Stocks: âNow, that which produces upward and downward movement is that which produces weight and lightness, and that which is moved is that which is potentially heavy and light, and the movement of each body to its own place is motion towards its own form.â
Theophrastus, De igne §â¯6, transl. Van Raalte:
Zeller (1963) II/1, 833.
Theophrastus, De igne §â¯1, 3â4, transl. Van Raalte:
Aristotle, De generatione et corruptione IÂ 7.
On the significance of this principle in Aristotleâs philosophy of life, see Rashed (2005), 133 n. 1. For a comparison of the role of this thesis in Aristotleâs and Theophrastusâ accounts of fire, see Federspiel (2017), 346â347. Notably, Federspiel called attention to Fr. 345 FHS&G, drawn from On Fainting, which illustrates the integration of this thesis into Theophrastusâ philosophy of life: âfainting is a loss or chilling of the warmth in the region where respiration occurs. This is brought about either by cold or even by warmth itself; for a larger fire extinguishes a smaller one.â
Regenbogen (1940), 1420: âMit Recht betont Gercke 31 gegenüber Zeller II 23, 832â¯ff. die eindringende Selbständigkeit dieser Fragestellungen gegenüber Aristoteles.â
Aristotle, De generatione animalium IIIÂ 4, 736b35â737a7, transl. Platt:
On Theophrastusâ circular aporetic approach to fire and heat in De igne, and the philosophical gain it yields, see Lefebvre (2017), 79â83.
Theophrastus, De igne §â¯7, 3â4, transl. Coutant:
These observations derive in part from Fabienne Baghdassarianâs response to my paper. Any errors are my own.
Gaiser (1985), 51.
Timaeus 58câd, transl. Cornford:
Topics V 5, 134b25â30, transl. W.A. Pickard-Cambridge: âSometimes, too, a man may even add the word âspecificallyâ, and still make a mistake. For the things in question should all be of one species, whenever the word âspecificallyâ is added; and in some cases this does not occur, as it does not, in fact, in the case of fire. For fire is not all of one species; for live coals (
Theophrastus, De igne §â¯3, 1â5, transl. Van Raalte:
Theophrastus, De igne §â¯1, 1â4, transl. Van Raalte:
Aristotle, De generatione et corruptione IIÂ 3, 330b25 and Meteorology IÂ 3, 340b23.
Theophrastus, De igne §â¯3, 9â11, §â¯4, 1â9, transl. Coutant:
Boureau (2022).
Aristotle, De juventute et senectute 5, 469b28â470a7, transl. G.R.T. Ross:
For example, Aristotle, De caelo IIIÂ 8, 307a24â26, and De anima IIÂ 4, 416a9â12. It is worth noting that the passage from De anima is commonly interpreted as addressing Heraclitus, with the expression
Aristotle, De caelo IIIÂ 8, 307a24â31, transl. Stocks:
As previously noted, Theophrastus acknowledges both of these characteristics, though he does not treat either as constitutive of fireâs essence.
Aristotle, De generatione et corruptione IIÂ 3, 330b21â26, transl. Joachim:
Aristotle, Meteorologica IÂ 3, 340b14â23, transl. Webster:
On this issue see Bodnár (2002b), 86â87.
Aristotle, Meteorologica IÂ 3, 340b26â27.
Aristotle, De caelo IVÂ 3, 310a32âb24.
Aristotle, De partibus animalium IIÂ 1, 646a12â20, transl. Ogle:
E.g. Paparazzo (2023) attempts to reconcile three distinct conceptions of fire in Meteorologica IâIII by associating them with different theoretical perspectives: fire as an element, as a form of exhalation, and as a combustion process.
This observation has been made, for example, by Van Raalte (2010), 49, in her commentary on De igne §§â¯1â10. However, it has often been interpreted in terms of Theophrastus rejecting metaphysical concerns, such as first principles, in favour of focusing on the everyday manifestations of fire (see the interpretations previously noted by Steinmetz 1964 and Battegazzore 1984).
On the relationship between elemental heat and fire in Theophrastusâ preserved works and fragments, see the discussion in Sharples (1998), 113â116.
Theophrastus, De igne §â¯53, 1â3, transl. Coutant:
As István Bodnár (2002b), 86, puts it: âTheophrastusâ discussion always links heat and the quality of hotness to processual and self-subsistent forms of fire. Heat apparently is a causally efficacious property (or even the causally efficacious property) of fire;
On this issue, see once again Lefebvre (2017), 79â83.
Plato, Timaeus 56aâb, transl. Cornford:
Aristotle, De caelo IIIÂ 8, 307b5â10, transl. Stocks:
Aristotle, De caelo IIIÂ 8, 307b6:
Theophrastus, De sensibus 87, 1â3, transl. Stratton (slightly modified):
Aristotle, De partibus animalium IIÂ 2, 648b35â649a17, transl. Ogle:
Theophrastus, De igne §â¯33, 1â6, transl. Coutant:
Steinmetz (1964), 135, considers the words between brackets as a gloss, added in order to bring Theophrastusâ text into line with the Aristotelian orthodoxy.
Theophrastus, De igne §â¯44, transl. Coutant.
See supra (p. 61â62), Aristotle, De partibus animalium II 2, 648b35â649a17.
Theophrastus, De igne §â¯54, transl. Coutant:
See Lloyd (1973), 10: âSimilarly On Fire hits on a fundamental objection to Aristotleâs doctrine on that subject. Yet Theophrastus attempts no new element theory, nor even a definite statement of what fire, in particular, is.â
This paper was written during my FWO Junior Postdoctoral Fellowship at KU Leuven (File no. 12ZI822N) and also forms part of a project funded by the European Research Council (ERC) under the European Unionâs Horizon 2020 research and innovation programme (Grant agreement no. 885273). The initial version of this paper was presented at a conference at the University of Lyon 3 in November 2022, organised by Gweltaz Guyomarcâh and Alessio Santoro. I am grateful to the organisers and participants for the engaging discussions, and especially to my respondent, Fabienne Baghdassarian, for her insightful and stimulating comments. Finally, I wish to thank the participants of the doctoral colloquium of the De Wulf-Mansion Centre at KU Leuven for the valuable feedback they gave on a later version of the paper.