Anaximenes: 'The Principle of All Things Is Air' — The Man Who Brought 'How' into Philosophy

Conclusion First (Key Takeaways)

• Introduction of Mechanism: Both Thales and Anaximander answered "What is the fundamental principle?" but failed to explain "How does everything arise from it?" Anaximenes was the first to present a quantitative mechanism of change — condensation (pyknōsis) and rarefaction (manōsis) — filling this gap.
• The Germ of Empirical Verification: The breath experiment (pursing the lips produces cold air; opening the mouth produces warm air) is one of the earliest instances of attempting to corroborate a theory through everyday experience. The correspondence of hypothesis and observation — here lies the prototype of the scientific method.
• Qualitative Change through Quantitative Change: A "quantitative" shift in the density of air produces "qualitatively" different substances — fire, water, earth. This idea is structurally identical to phase transitions in modern physics (water becoming ice or steam) and quantization in information theory.
• The Completion of the Milesian School: Thales asked "What," Anaximander asked "Why," and Anaximenes asked "How." This deepening of inquiry across three generations is the prototype of a research program in any field of study.

Life and Historical Context

Anaximenes was born around 585 BCE in Miletus, a port city in the Ionian region. According to Theophrastus's testimony (via Simplicius), he was a "companion (hetairos)" of Anaximander and is traditionally placed as the third generation of the Milesian school (Diogenes Laërtius, Lives II.3). However, the term "student" originates with Theophrastus, and whether it denotes a strict teacher–pupil relationship or a younger member of the same intellectual tradition remains uncertain. Note that the similarly named "Anaximenes of Lampsacus" (c. 380 – c. 320 BCE), a rhetorician who accompanied Alexander the Great, is a different person separated by about 200 years. Care is needed, as they are sometimes confused in ancient sources.

Miletus in the latter half of the 6th century BCE, when Anaximenes was active, was in the midst of major geopolitical upheaval. In 547/546 BCE, Cyrus the Great of Persia destroyed King Croesus of Lydia, and the Ionian region came under Persian rule. Given that both Thales and Anaximander are said to have died around 546 BCE, Anaximenes belonged to the last generation of Miletus's intellectual golden age. His philosophical work was carried out amid the political turmoil of Persian domination. In 494 BCE, the suppression of the Ionian Revolt dealt a devastating blow to Miletus, effectively ending the Milesian school's intellectual tradition. Anaximenes was the last great philosopher active just before that end.

Miletus's character as a trading city remained unchanged. Knowledge flowing in through commerce with Egypt, Babylonia, and Phoenicia — especially Babylonian astronomical observation data and empirical knowledge of meteorology — may have influenced Anaximenes's focus on "air." In ancient Mesopotamia, records of wind directions and weather changes had been accumulated (the Enūma Anu Enlil text corpus), and the notion that air, wind, and breath are deeply connected to life was widespread in the Near East. Just as the Hebrew word "ruach" (רוח) carries three meanings — "wind," "breath," and "spirit" — the identification of "invisible gas" with "the principle of life" was widely shared across the ancient Mediterranean world.

Anaximenes is also said to have written a work entitled On Nature (Peri Physeōs) (Diogenes Laërtius, Lives II.3). According to that source, he wrote in "plain and unadorned Ionic dialect (ἁπλῇ καὶ ἀπερίττῳ Ἰάδι)." Diogenes took the trouble to record this stylistic feature, possibly drawing a contrast with the (presumably more obscure) prose of his master Anaximander. The work itself is lost, and only three fragments survive (DK 13 B1, B2, B3). Among the three Milesians — Thales, Anaximander, and Anaximenes — the personal profile of Anaximenes is the thinnest. No anecdotes comparable to the non-philosophical exploits of his predecessors (Thales's eclipse prediction and olive-press business, Anaximander's world map and colonization expedition) have come down to us, and posterity remembered him simply as a "man of theory."

Mini Timeline

• c. 585 BCE: Born in Miletus, Ionia
• 560s BCE: Studies natural philosophy under the influence of Anaximander
• 547/546 BCE: Persia conquers Lydia; Ionia falls under Persian rule
• c. 546 BCE: Thales and Anaximander die; Anaximenes carries on the Milesian school
• 540s–530s BCE: Writes On Nature; systematizes the air-as-archē theory and the condensation/rarefaction mechanism
• c. 528/525 BCE: Dies in Miletus

What Did Anaximenes Ask?

The problem Anaximenes confronted was the "unfinished homework" left by his two Milesian predecessors. Thales had claimed that "the fundamental principle of all things is water," but he did not explain the process of change — how fire or earth could arise from water. Anaximander avoided the problem of opposites by making the fundamental principle "the Boundless" (to apeiron). However, "the Boundless" could not be grasped by the senses, and how concrete substances could arise from it remained unclear.

In other words, the Milesian school had two gaps. First, it had answered "What is the fundamental principle?" but not "How does it change?" Second, Anaximander's "to apeiron," while logically refined, was difficult to grasp empirically and lacked concrete explanatory power.

Anaximenes's strategy was to fill both gaps at once. By returning the fundamental principle to a concrete substance — air — he restored empirical accessibility, and by simultaneously introducing the principle of change through "condensation and rarefaction," he explained the process by which all substances arise from a single substance. Presenting "what it is" and "how it changes" as a single unified account — this was Anaximenes's innovation.

The significance of this shift is profound. In modern science, "what something is" (ontology) alone is insufficient as a scientific explanation; describing "by what mechanism it changes" (process description) is indispensable. Darwin's theory of evolution demonstrating the mechanism of "natural selection," Newton's formulation of the dynamics of "universal gravitation" — all of these are answers to "How." Anaximenes was the first person to bring this "How" into philosophy.

Core Theories

1. Air (Aēr) — Why Return to a Concrete Substance?

The fundamental principle Anaximenes chose was "air (ἀήρ / aēr)." However, an important terminological note is necessary here. The ancient Greek word ἀήρ differs considerably in meaning from the modern word "air" — a transparent, dry gas. In Homer and Hesiod, ἀήρ meant "mist," "haze," "dark vapor," while the transparent atmosphere was called αἰθήρ (aithēr) (Kirk & Raven, 1983, pp. 144–145). Anaximenes's "aēr" should likewise be understood not as the colorless, transparent gas we picture in everyday life, but rather as an invisible yet world-filling, mist-like, moist gaseous entity. This understanding highlights the naturalness of the process by which air condenses to become "clouds → water" — it is precisely the process of mist condensing into rain.

According to Theophrastus's report (Simplicius, Commentary on the Physics 24.26–25.1), Anaximenes held that air is "boundless (apeiron)" while identifying its surrounding qualities as "air." In other words, he did not completely reject Anaximander's "indeterminacy" but rather gave the boundless a concrete identity.

Why air? Several reasons may be inferred. First, air is invisible (or, like mist, semi-transparent) yet exists everywhere. Unlike Thales's "water," it is not limited to specific locations but fills the entire world. Second, air is directly connected to life — if one stops breathing (pneuma / πνεῦμα), one dies. Anaximenes's surviving fragment B2 makes this analogy explicit:

"Just as our soul, being air, holds us together, so do breath (pneuma) and air encompass the whole cosmos." — Aëtius, Placita I.3.4 (DK 13 B2). However, there are several textual variants for this fragment, and whether the phrase "soul is air" is Anaximenes's own expression or a later interpretation is debated.

What we see here is the analogy between microcosm (human being = small universe) and macrocosm (world = great universe). Just as the human body is sustained by breathing (air), the entire cosmos is sustained by air. This analogy was later inherited by Plato (Timaeus) and Stoic cosmology, and serves as one of the starting points of a grand intellectual lineage flowing through medieval Neoplatonism and on into Renaissance natural philosophy.

Third, air can to some extent circumvent Anaximander's critique of Thales — "one member of an opposition cannot serve as the fundamental principle." Air possesses an "intermediate" quality, being capable of being both cold and warm, and is not fixed to either water or fire. Anaximenes's choice was a compromise between concreteness and the indeterminacy of the apeiron.

2. Condensation (Pyknōsis) and Rarefaction (Manōsis) — The First Mechanism of Change

Anaximenes's greatest innovation was making explicit the mechanism by which all things arise from a single substance, air. This mechanism is "condensation (πύκνωσις / pyknōsis)" and "rarefaction (μάνωσις / manōsis)" (Theophrastus, Simplicius, Commentary on the Physics 24.26–25.1; pseudo-Plutarch, Stromateis ch. 3).

When air rarefies, it becomes hotter and lighter, eventually becoming fire. Conversely, when air condenses, first wind is produced; further condensation yields clouds, water, earth, and stone. In other words, merely by changing the density of air — without introducing any additional principle — all substances in the cosmos are explained:

Fire ← rarefaction ← Air → condensation → Wind → Clouds → Water → Earth → Stone

In Aëtius's testimony (Placita I.3.4), the term used for this condensation process is πίλησις (pilēsis). This derives from the craft of compressing wool into felt (pilos) — a metaphor drawn from the everyday technique of pressing fibers together to create a material of different texture. Miletus was one of the ancient world's leading wool-industry cities, and Anaximenes's choice of this metaphor may reflect the experiential knowledge of local industry.

This theory's innovativeness lies in three aspects.

First, continuous change. From fire to stone, the types of substance form an unbroken continuum. Differences in kind are not differences in essence but merely differences in the "degree" of density. This is an intuitive anticipation of phase transitions in modern physics (water changing to ice or steam depending on temperature).

Second, the germ of quantification. The change of "denser/thinner" is in principle open to the quantitative question of "how much denser/thinner?" Anaximenes himself did not perform numerical quantification, but the attitude of treating change as a quantitative continuum rather than a qualitative leap is a distant headwater of the Pythagorean school's mathematical view of nature and of modern science's quantitative methodology.

Third, the unity of mechanism. The entire diversity of things is explained by "a single principle of change" — condensation and rarefaction. No additional principles or forces are introduced. This theoretical parsimony (the spirit of Occam's Razor) is at the heart of the virtues of scientific theory.

3. The Breath Experiment — The Earliest Attempt at Empirical Verification

To corroborate his theory, Anaximenes presented a remarkable "experiment." Transmitted in the surviving fragment B1 (pseudo-Plutarch, Stromateis ch. 3), this episode is known as one of the earliest attempts at empirical verification in the history of science.

Purse your lips and blow — the air that comes out is cold. Open your mouth wide and breathe "haa" — the air that comes out is warm. Anaximenes interpreted this everyday observation as follows: when one blows with pursed lips, the air is compressed (condensed) and becomes cold; when one breathes with an open mouth, the air spreads out (rarefies) and becomes warm. This, he argued, is empirical evidence for his theory — that condensation produces cooling and rarefaction produces heating.

From the perspective of modern physics, this explanation is actually incorrect. The air feels cold when blown through pursed lips because the increased flow velocity entrains surrounding air (the entrainment effect), mixing in room-temperature air cooler than body temperature — not because of adiabatic expansion or compression. Breathing "haa" feels warm because the slowly exhaled air remains close to body temperature.

However, the significance of the method matters more than the correctness of the conclusion. Anaximenes attempted to verify a cosmological theory through everyday bodily experience. "If the theory is correct, this phenomenon should be observed" — this structure of hypothetico-deductive reasoning is the prototype of the scientific method that Francis Bacon and Galileo would not formalize until over 2,000 years later. The result was wrong, but the approach was right.

4. Cosmology — A Flat Earth and an Aerial Cosmos

Anaximenes's cosmology is constructed as a natural consequence of his air-as-archē theory. According to testimonies from Hippolytus (Refutation of All Heresies I.7) and Aëtius (Placita, Books II–III), the earth is flat and disc-shaped, floating on air — just as a leaf is held aloft by the wind. Compared with Anaximander's sophisticated argument of "rest through equidistance," this may appear to be a somewhat naïve regression.

Anaximenes also held distinctive views on the celestial bodies. The stars are not the most distant objects from earth but are like "studs" — fiery bodies embedded in the air (Aëtius, Placita II.14.3–4). The sun is flat and moves around the earth not by passing under it but by revolving around it like a cap around the head. Night falls not because the sun sinks below the earth but because it is hidden behind the earth's higher regions.

This cosmology may appear to be a retreat compared to Anaximander's concentric-ring model. However, the theoretical consistency of attempting to explain everything through "air and its varying density" deserves recognition. The earth floats, the celestial bodies shine, clouds and rain form — all explained as behavior of air in a unified framework.

Particularly noteworthy is Anaximenes's systematic explanation of meteorological phenomena. According to testimonies from Aëtius (Placita, Book III) and Hippolytus (Refutation of All Heresies I.7), he argued as follows. Rain occurs when air condenses to form clouds, which are further compressed to fall as water. If condensation intensifies further, it becomes hail; snow is water solidified with an admixture of air (wind). Rainbows occur when sunlight strikes dense clouds. Earthquakes result from the earth drying out excessively and cracking, or conversely becoming excessively moist and collapsing — both ultimately attributable to the condensation and rarefaction of moisture in the air. Thunder and lightning occur when wind tears clouds apart. Individually, these explanations are inaccurate, but the innovative point is the attempt to derive all of them from a single principle — changes in the density of air. This is an intellectual attitude fundamentally different from mythological explanations that invoke a separate deity for each phenomenon.

5. The Isomorphism of Soul and Cosmos — Macrocosm and Microcosm

The equation "soul = air, cosmos = air" presented in Fragment B2 carries theoretical implications beyond mere metaphor. If the principle sustaining human life (breathing = air) and the principle sustaining the cosmos (archē = air) are one and the same substance, then understanding the human being is directly connected to understanding the cosmos, and vice versa.

This macrocosm = microcosm idea became a powerful motif recurring throughout the history of Western thought. Plato's Timaeus depicts the cosmos as a "great living being"; the Stoics made pneuma (breath/spirit) the governing principle of the universe. In the Renaissance, Paracelsus conceived of medicine by treating the human body as a microcosm of the universe, and in the 20th century James Lovelock theorized the entire Earth as a self-regulating system (the Gaia hypothesis).

Modern fractal theory — in which parts and wholes share self-similar structures — is also a mathematical expression of the intuition that worlds at different scales share isomorphic structures. Anaximenes's equation of soul = air is one of the starting points of this grand lineage.

Key Works Guide

Anaximenes's writings have been lost; only three fragments survive (DK 13 B1, B2, B3). The following is a guide to the literature for reconstructing his thought.

• Introductory: Diogenes Laërtius, Lives of the Eminent Philosophers, II.3 — A concise biographical overview of Anaximenes's life and achievements. The starting point for understanding the relationship among the three generations of the Milesian school.
• Introductory: Patricia Curd & Daniel W. Graham, eds., The Oxford Handbook of Presocratic Philosophy, Oxford UP, 2008 — An accessible overview of the Milesian school, clearly tracing the intellectual development from Thales to Anaximander to Anaximenes.
• Intermediate: Aristotle, Metaphysics, Book I, 984a — Aristotle's systematic analysis of the archē theories of the early natural philosophers, including references to Anaximenes.
• Advanced: G. S. Kirk, J. E. Raven, M. Schofield, The Presocratic Philosophers, 2nd ed., Cambridge UP, 1983, Ch. 5 — A critical examination of all of Anaximenes's fragments and testimonies. Provides the most detailed discussion of the interpretive problems surrounding the condensation/rarefaction mechanism.
• Advanced: D. W. Graham, Explaining the Cosmos: The Ionian Tradition of Scientific Philosophy, Princeton UP, 2006, Ch. 3 — An important recent work reassessing the scientific thinking of the Milesian school, focusing on Anaximenes's methodological innovation.

Major Criticisms and Debates

1. Heraclitus's Critique (Contemporary/Successor): Heraclitus of Ephesus is sometimes regarded as having been skeptical of the entire Milesian enterprise of identifying "a single fundamental substance." For him, what mattered was not the identity of the substance but the perpetual process of opposition and change itself. Although Heraclitus is said to have posited "fire" as the archē, his fire was more a symbol of change than a substance — a discourse on a different plane from Anaximenes's "air."

2. Aristotle's Evaluation and Critique (Later): Aristotle understood Anaximenes's condensation/rarefaction theory as "change through opposing qualities" (Physics I.4, 187a12–23) and granted it a measure of recognition as a precursor to his own theory of material change. In Metaphysics I.3 (984a5), he explicitly mentions Anaximenes as the philosopher who held "air as the principle of all things." However, he also criticized Anaximenes for failing to explain "why air changes" — the efficient cause of change. Air condenses and rarefies, but what is the force that drives this change? Anaximenes implicitly assumed that "eternal motion" is inherent in air, but Aristotle regarded this as an unproven assumption.

This critique is based on Aristotle's own "four causes" — especially the demand for efficient and final causes. Whether it fairly evaluates Anaximenes's argument is open to question.

3. Modern Interpretive Debates: Scholars are divided on whether Anaximenes's theory represents "regression" or "progress." (a) Burnet (1892) and Guthrie (1962) viewed the return to a concrete substance as a "regression" from Anaximander's abstract thinking. (b) On the other hand, Kirk & Raven (1983) and Graham (2006) emphasize the introduction of mechanism and evaluate it as "progress" in scientific methodology. (c) More recently, scholars such as Lewis (2009) have attempted to reevaluate Anaximenes's theory within the broader context of "early Greek matter theory," moving beyond the regression/progress dichotomy.

Influence and Legacy

Antecedent Thought: Thales's archē inquiry (the framework of asking "What?"), Anaximander's to apeiron (the idea of indeterminacy and the separation of opposites), Babylonian meteorological records (empirical knowledge of wind and weather). Anaximenes critically synthesized the questions and answers of his two predecessors.

Direct Successors: Diogenes of Apollonia (later 5th century BCE) explicitly inherited Anaximenes's air-as-archē theory and attempted a synthesis with Anaxagoras's Nous (Mind) by attributing "intelligence (noēsis)" to air. Simplicius (Commentary on the Physics 151.31) described Diogenes as "almost an imitator of Anaximenes." In Aristophanes's comedy The Clouds (first performed 423 BCE), Socrates is caricatured as worshipping "air" and "vortex" — this is generally understood to be a parody of the teachings of Diogenes, then well known in Athens. In other words, Anaximenes's thought, through his direct successors, had permeated even Athenian popular culture.

Bridge to Empedocles and Pluralism: Anaximenes's model of "many substances arising from one" prepared the preconditions for Empedocles's "four-element theory" (earth, water, air, fire) in the 5th century BCE. Empedocles abandoned monism for pluralism, but his list of elements — "air," "water," "fire," "earth" — can be seen as the substances that Anaximenes had arrayed on the spectrum of condensation and rarefaction, now promoted to independent fundamental principles.

Influence on the Stoics: The Stoics (from the 3rd century BCE) developed a theory in which "pneuma (breath/spirit)" serves as the governing principle of the cosmos. Pneuma was "a mixture of fire and air" that pervaded the entire cosmos, imparting tension (tonos) and unity. The two motions of "expansion and contraction" in Chrysippus's (3rd century BCE) pneuma theory show a striking structural similarity to Anaximenes's "rarefaction and condensation." Whether Anaximenes's equation of "soul = air" and "cosmos = air" flowed directly into Stoic pneuma theory is debated, but indirect influence through Posidonius (1st century BCE) and Seneca (1st century CE) is widely recognized.

Reach into the History of Science: The idea of condensation and rarefaction as a mechanism structurally corresponds to the "gas laws" of modern chemistry (Boyle's Law: the inverse relationship between pressure and volume, 1662) and phase-transition theory in physics. The model that "a single substance exhibits different states through changes in density" was first presented by Anaximenes 2,600 years ago and was only precisely formulated by modern science.

The Completion of the Milesian School — The Legacy of Three Thinkers

With Anaximenes's death, the Milesian school's approximately eighty-year intellectual tradition drew to a close. If we organize the questions and methods left by the three, the full picture of their collaborative endeavor comes into view. Thales asked "What is it?" (What), Anaximander asked "Why must it be so?" (Why), and Anaximenes asked "How does it change?" (How). What → Why → How — this three-stage deepening is the prototype of inquiry in every field of study.

The Milesian school established a framework for naturalistic, rational explanation of the world as an alternative to mythological explanation. After them, Greek philosophy exploded in its exploration of the question "What is the fundamental principle of all things?" — Heraclitus's fire, Pythagoras's number, Parmenides's Being, Empedocles's four elements, Anaxagoras's Nous, and Democritus's atom. This entire grand intellectual competition stands on the horizon of questioning opened up by the three Milesians.

Connection to the Present

Anaximenes's legacy lives on in the present across two — indeed, three — dimensions.

First, "the demand for mechanism." In modern science, merely showing "what something is" is insufficient; a mechanism explaining "how it comes to be" is required. Darwin presented not just the "fact" of evolution but the mechanism of "natural selection"; Watson and Crick revealed not just the "structure" of DNA but the "mechanism of replication." The progress of science is always a deepening of "How." Anaximenes was the first to satisfy this demand 2,600 years ago.

Second, the idea that "quantitative change produces qualitative change." Water becomes ice at 0°C and steam at 100°C. The same H₂O molecule takes on "qualitatively" entirely different forms through a change in the "quantitative" parameter of temperature. Marx's "transformation of quantity into quality" (derived from Hegelian dialectics) in Capital, the chain reaction that begins when critical mass is exceeded in nuclear physics, and the ecological "tipping points" at which the behavior of an entire system changes abruptly once a threshold is crossed — in all of these, the echo of Anaximenes's intuition can be heard. "More" becomes "something entirely different" — the first to explicitly articulate this astonishing principle was Anaximenes's theory of condensation and rarefaction.

Third, its significance as the prototype of "monistic reductionism." The "Theory of Everything" pursued by modern physics — describing gravity, electromagnetism, the strong force, and the weak force within a single framework — shares the same structure as Anaximenes's intellectual drive to "reduce the diversity of the world to a single principle." To be sure, the mathematical sophistication of modern physics and Anaximenes's naïve air-monism are beyond comparison.

But the conviction that "the world cannot be as complex as it appears" and that "there must be a simple unifying principle behind it" — this deepest motivation driving science was first articulated by the three Milesians, and above all by Anaximenes, who presented a self-contained system of "one substance + one mechanism."

Questions for the Reader

• In your own field of expertise, what is a problem where "what it is" is known but "how it comes to be" has yet to be elucidated? Following Anaximenes's lead, try posing the question of "How."
• Have you ever had an experience where quantitative change triggered qualitative change — for example, where accumulated practice suddenly turned into "being able to do it" one day? How might this be explained by analogy with "condensation and rarefaction"?
• Anaximenes's breath experiment reached the wrong conclusion but took the right approach. In the history of science, there are countless cases where a correct methodology produced an incorrect conclusion that was later corrected, bringing us closer to the truth. In your own work or studies, have you had an experience where "the method was right but the conclusion was wrong"? What did you learn from that experience?
• Thales asked "What is it?", Anaximander asked "Why must it be so?", and Anaximenes asked "How does it change?" At which stage — What, Why, or How — is the problem you are currently facing? What should you ask next?

References

• Primary Source (Fragments and Testimonies): H. Diels & W. Kranz, eds., Die Fragmente der Vorsokratiker, Vol. 1, chapter on Anaximenes (DK 13). Contains Fragments B1–B3 and all testimonies (A section).
• Primary Source (Testimonies): Aristotle, Metaphysics, Book I — References to Anaximenes around 984a5; Simplicius, Commentary on the Physics 24.26–25.1 — The most detailed testimony via Theophrastus.
• Primary Source (Biography): Diogenes Laërtius, Lives of the Eminent Philosophers, II.3.
• Secondary Source (Standard Reference): G. S. Kirk, J. E. Raven, M. Schofield, The Presocratic Philosophers, 2nd ed., Cambridge UP, 1983, Ch. 5 — The standard reference, offering the most rigorous examination of Anaximenes's fragments and testimonies.
• Secondary Source (Scientific Methodology): D. W. Graham, Explaining the Cosmos: The Ionian Tradition of Scientific Philosophy, Princeton UP, 2006 — An important recent work reassessing the scientific thinking of the Milesian school; details the significance of Anaximenes's introduction of mechanism.
• Secondary Source (New Edition of Fragments): A. Laks & G. W. Most, eds., Early Greek Philosophy (Loeb Classical Library 524–532, Harvard UP, 2016) — A new standard edition replacing DK. Contains all fragments and testimonies of Anaximenes with facing Greek text and English translation.
• Secondary Source (Classic Study): J. Burnet, Early Greek Philosophy, 4th ed., A&C Black, 1930 (first ed. 1892) — Representative of the classic interpretation that evaluated Anaximenes as a "regression." Now revised, but important for the history of scholarship.
• Secondary Source (General History): W. K. C. Guthrie, A History of Greek Philosophy, Vol. 1, Cambridge UP, 1962 — A comprehensive history covering the entire Milesian school. Follows Burnet's assessment while making revisions.
• Secondary Source (Handbook): P. Curd & D. W. Graham, eds., The Oxford Handbook of Presocratic Philosophy, Oxford UP, 2008 — Surveys the latest research trends in early Greek philosophy, including multiple essays on Anaximenes's methodological innovation.