1. Life
Diogenes' life is known through scattered accounts from ancient sources, revealing details of his origins and his activities in Athens.
1.1. Background and Early Life
Diogenes of Apollonia was a native of the Milesian colony Apollonia Pontica, located in Thrace, which corresponds to modern-day Sozopol on the Black Sea. While this is the widely accepted view, an alternative perspective suggests that the Apollonia in question might have been the Cretan city that was originally Eleutherna, though this view is not commonly accepted by modern scholars. His father's name was Apollothemis.
Little is definitively known about the events of Diogenes' early life. According to the testimony of Antisthenes, Diogenes was a pupil of Anaximenes, indicating a possible intellectual lineage tracing back to the Ionian tradition. He was also a contemporary of Anaxagoras, suggesting he was active during a significant period of philosophical development in ancient Greece, around 430-420 BC, or possibly as early as 460 BC. Despite his Dorian origin, Diogenes, like other *physiologoi* (natural philosophers), wrote his philosophical works in the Ionic dialect, a characteristic common among the early natural philosophers.
1.2. Activities in Athens
Diogenes lived and engaged in intellectual activities for some time in Athens. Historical accounts suggest that his presence and philosophical views in the city led to considerable tension. Diogenes Laërtius reports that "great jealousy nearly put his life in danger in Athens." This threat to his life may have been due to strong opposition from his philosophical adversaries or possibly due to his perceived atheism, as suggested by some sources. There is also a possibility that the accounts of threats to his life in Athens might be confused with similar experiences faced by Anaxagoras, who is mentioned in the same historical passage by Diogenes Laërtius.
2. Philosophy
Diogenes of Apollonia's philosophical system primarily focused on the nature of the fundamental principle of the universe, extending his theories to cosmology, the nature of living beings, and human physiology.
2.1. Air as the Fundamental Principle
Diogenes of Apollonia's central philosophical tenet was that air is the singular, fundamental source of all existence. This idea shares a strong resemblance with the views of Anaximenes, another influential Presocratic philosopher who also posited air as the primary element. Diogenes further developed this concept by integrating it with theories from his contemporary, Anaxagoras, and asserting that air, as the primal force, was not only intelligent but also divine.
He argued that all other substances in the universe are derived from air through processes of condensation and rarefaction. Conversely, all existing things will eventually return to air. This belief was rooted in his conviction that "what exists cannot be made from nothing, therefore what exists cannot become nothing." Diogenes maintained that the nature of the universe is air, describing it as limitless and eternal. In his words, "And it seems to me that that which possessed thought is what people call air, and that by this everyone both is governed and has power over everything. For it is this which seems to me to be god and to have reached everything and to arrange everything and to be in everything. And there is not a single thing which does not share in it." He thereby established a unique form of material monism, diverging from the Atomists and avoiding the dualism proposed by philosophers like Empedocles.
2.2. Cosmology
Diogenes' cosmological theories were a direct extension of his belief in air as the fundamental principle. He proposed that the universe itself, along with all its components, came into being through the processes of condensation and rarefaction of air, as air changes its properties.
He held a comprehensive view of the cosmos, believing in the existence of an infinite number of worlds and an infinite void. In his view, the different worlds were formed as air densified and rarefied. Diogenes also offered an explanation for the Earth's physical characteristics. He stated that the Earth is round and centrally supported. Its spherical shape was believed to have formed from the whirling motion of warm vapors, while its concretion and hardening were attributed to the effects of cold.
2.3. On Living Beings
Diogenes extensively discussed the essential role of air in the existence and cognitive functions of living creatures. He contended that air is indispensable for both humans and animals, not only for their physical existence but also for the maintenance of their souls and their capacity for thought. According to his theory, if air were to cease entering a living being, that creature would die and its ability to think would cease.
He further posited that the distinctions between different living beings, including various animals and humans, stem from the varying properties and temperatures of the air contained within them. For instance, Diogenes suggested that the air inside animals is generally warmer than the external air but cooler than the air found in the sun. Similarly, he believed that differences among various animal species, and even among individual humans, could be attributed to the unique characteristics of the air within them.
2.4. On Human Physiology
Diogenes of Apollonia also delved into human anatomy and physiology, offering insights that reflect a nascent scientific approach. His most extensive surviving fragment details the distribution of blood vessels throughout the human body, providing a rare first-hand account of early Greek attempts to describe the physical world in scientific detail.
He described the existence of two large blood vessels in humans. These vessels reportedly extended through the abdomen along the spine, with one on the right side and the other on the left. From these main vessels, branches continued into the arms and ascended through the throat. Furthermore, he observed that the blood vessels branched out across the entire body, with the right vessel supplying the right side of the body and the left vessel supplying the left side. He also noted that these two large vessels passed through the heart, indicating a foundational understanding of the circulatory system's layout, even if incomplete by modern standards.
Diogenes also connected air to states of health, illness, and sensory experiences. He theorized that feelings of pleasure arose when a sufficient amount of air mixed with blood, rendering the blood light. Conversely, illness occurred when air did not properly mix with the blood, causing the blood to become thick and weaker.
His physiological insights extended to cognitive functions. He proposed that infants have limited thinking abilities because large amounts of vapor within their bodies prevent air from fully pervading their system, causing it to remain largely confined to the chest. Similarly, he attributed the phenomenon of forgetting to air not properly entering the entire body. As evidence for this, he noted that when individuals attempt to recall something, their chest contracts, and upon successfully remembering, there is a sensation of relaxation and relief.
3. Works
Diogenes of Apollonia's philosophical contributions are primarily known through surviving fragments, as his complete works have not endured to the present day.
3.1. Surviving and Lost Works
None of Diogenes of Apollonia's philosophical writings have survived in their complete form. His principal work is widely considered to be *On Nature* (De naturaLatin), which encompassed his cosmological, physical, and physiological theories. Scholars debate whether *On Nature* was a single comprehensive treatise that included sections on specific topics, or if he authored separate works such as *On the Nature of Man*, *Meteorology*, and *Against the Sophist*. The consensus among modern scholars suggests that these other titles likely refer to parts or sections within his larger work *On Nature*.
The majority of the surviving fragments of Diogenes' work come from quotations by later philosophers, most notably Simplicius of Cilicia. Simplicius, a Neoplatonic philosopher from Late Antiquity, extensively quoted Diogenes in his commentary on Aristotle's *Physics*, thus preserving significant portions of Diogenes' original thought. Other ancient sources, including Aristotle, Theophrastus, and Aetius, also provide summaries and references to his doctrines.
4. Legacy and Reception
Diogenes of Apollonia's philosophical ideas elicited various responses in antiquity and have experienced a complex reception in modern scholarship, marked by periods of neglect and recent rediscovery.
4.1. Ancient Reception and Influence
In ancient times, Diogenes' ideas were a subject of both philosophical discussion and satirical commentary. His views are widely believed by modern scholars to have been caricatured and attributed to Socrates in Aristophanes' famous comedy, *The Clouds*. This satirical portrayal also appears in fragments from the poet Philemon.
Furthermore, Diogenes of Apollonia is remembered for his early speculation on the extraterrestrial origin of meteorites. He proposed that "With the visible stars revolve stones which are invisible, and for that reason nameless. They often fall on the ground and are extinguished, like the stone star that came down on fire at Aegospotami." This prescient idea led to the naming of diogenite meteorites in his honor.
4.2. Modern Studies and Rediscovery
For a considerable period in modern scholarship, Diogenes of Apollonia's work was relatively neglected, a trend observed and noted by early scholars like Hermann Diels. However, interest in his philosophy has seen a significant resurgence in recent decades, largely due to the discovery of the Derveni Papyrus.
The Derveni Papyrus, an Orphic philosophical poem, contains notable parallels to the philosophies of both Diogenes and Anaxagoras. Its discovery has prompted numerous scholars to re-examine Diogenes' work, leading to new analyses and a deeper understanding of the complex links between Ancient Greek religion and philosophy. This rediscovery has highlighted Diogenes' unique position in Presocratic thought and his contributions to the intellectual landscape of ancient Greece.