Miletus is in present-day Turkey.

The Enlightenment Attitude

Thales (second half of the 7th century and the first decades of the 6th century BCE)
Anaximander (middle of the 6th century BCE)
Anaximenes (middle of the 6th century BCE, a little after Anaximander)

Trade in the Eastern Mediterranean Basin was making it increasingly clear that there were different ways of life and beliefs about the world. In the light of these alternatives, the received wisdom and traditional practices no longer seemed so obviously correct. At the same time, there was confidence that knowledge of the truth about things was possible if instead of accepting the authority of traditional thought, individuals were to think clearly for themselves. In this way, in the ancient Greek city of Miletus, the circumstances were right for the introduction of a new, more objective way of thinking about the world and the place of human beings in it.

Hesiod and the Theologists

Hesiod (middle of 8th century BCE to middle of the 7th century BCE, younger contemporary of Homer).

His Theogony and Works and Days) are the earliest examples Greek "didactic" poetry. (The adjective διδακτικός means "apt at teaching, educational"). Theogony describes the origin of the world and the genealogies of the gods. Works and Days describes daily life and work in an agricultural setting against the background of a religious calendar.

In the history of Greek thought, Hesiod represents the older and traditional way of thinking about the world and the place of human beings. This way of thinking about the world conceives of things in terms of the pantheon of traditional gods. The following is an example of the sort of understanding that characterizes this tradition:

"Zeus who thunders aloft..." (Hesiod, Works and Days 8).

(1) Rain is a manifestation of the mind of Zeus.
(2) Zeus wills that it rain.
(3) It is raining.

Rain is a way that Zeus shows himself to human beings.

"The school of Hesiod, and all the theologists (θεολόγοι), ... make the starting-points (ἀρχὰς) gods or generated from gods" (Aristotle, Metaphysics III.4.1000a).

Thales and the Milesian Naturalists

The Milesian inquirers into nature (Thales, Anaximander, Anaximenes) exemplify the enlightenment tradition that was taking root in the ancient world. Instead of relying on the traditional thought and received wisdom represented by the older school of Hesiod and the theologists, Thales and his fellow Milesian inquirers tried to think about and explain things in a new way.

"Thales, the founder of this sort of philosophy (φιλοσοφίας), says that [the starting-point (ἀρχή) underlying all things] is water..." (Aristotle, Metaphysics I.3.983b).

"Of those who say that the starting-point (ἀρχήν) is one and movable, to whom Aristotle applies the distinctive name of physicists (φυσικοὺς), some say that it is limited; as, for instance, Thales of Miletus, son of Examyes, and Hippo who seems also to have lost belief in the gods. These say that the starting-point is water..." (Simplicius, following Theophrastus, Commentary on Aristotle's Physics IX.23.21).

(The Latin principium is a translation of the Greek ἀρχή. For this reason, ἀρχή sometimes is translated into English as 'priniciple.')

Thales and the Milesian inquirers tried to explain "natural" phenomena (as we now describe the phenomena in our debt to them) in terms of changes in the "nature" (φύσις) of reality. Their effort became known as the "inquiry into nature" and their explanations were different in style from those in the older school of thought represented by Hesiod and the theologists. (The evidence for this interpretation depends primarily on Aristotle. He refers to Thales and the Milesians as φυσιολόγοι and the theologists as θεολόγοι (Metaphysics I.5.986b14; Metaphysics III.4.1000a9), as "those who talk about nature" and "those who talk about the gods." Because virtually nothing has survived of what Thales and the Milesians wrote, it is uncertain how they themselves described their inquiries.)

(The noun φύσις is the etymological root of the English word physics. The translation into English as nature is through the translation of the Greek word into Latin as natura.)

(Thales, Anaximander, and Anaximenes were from the city of Miletus in Asia Minor on the coast of the Aegean Sea. The lines of influence are not easy to reconstruct, but subsequent intellectual activity within the Presocratic Period seems to have spread out from Miletus. The use of the description 'Presocratic' originates with the German scholar, Hermann Diels. His magisterial collection of the evidence for early Greek philosophy, first published in 1903, is entitled Die Fragmente der Vorsokratiker (The Fragments of the Presocratics). This description, although now traditional, can be a little misleading because it can suggest that the Presocratics lived before Socrates. In fact, he overlapped with some of them, and one, at least, Democritus, seems to have outlived him.)

(Theophrastus succeeded Aristotle as head of the Lyceum. Aristotle and Theophrastus are the source for most of what is known about the "beliefs" (δόξαι) of the Presocratics.)

The New Explanations in terms of Nature

The inquiry into nature turned out to be very important in the history of the world.

In the new school of thought represented by the inquirers into nature, explanations do not make reference to the gods. The new explanations explain natural phenomenon in terms of the nature of reality. This is an attempt to identify the "starting-points" (ἀρχαί) in reality and to explain whatever there is in terms of these starting-points.

The following is an example of an explanation in this new style:

"Anaximenes... declares that the underlying nature... is air. It differs in rarity and density according to the things that it becomes. Becoming finer it comes to be fire; being condensed it comes to be wind, then cloud, and when still further condensed it becomes water, then earth, then stones, and the rest come to be out of these" (Simplicius, Commentary on Aristotle's Physics = DK 13 A 5).

(1) Rain is condensed air.
(2) The air here is now condensed.
(3) It is raining.

There is no mention of the mental life of a god. Instead, the explanation is in terms of (what Anaximenes takes to be) the nature of reality.

(Sometimes the older explanations of Hesiod and the theologists are said to be "mythological" and the newer explanations of Thales and the Milesian naturalists are said to be "rational." This terminology can be a little misleading. It can suggest that the older explanations do not make sense because they are not based on reason. In Metaphysics III.4.1000a, Aristotle talks this way about the explanations of Hesiod and the theologists. There is clearly something right about Aristotle's characterization, but this way of putting the contrast between the older and newer explanations can overstate the point. Reason had been used for all sorts of practical and intellectual purposes in the history of humankind, but it lacked the independence from religion and the status necessary to challenge the most traditional beliefs about the world and human beings. The Milesian inquiries into nature are an example of the change in the status of reason that was taking place in the ancient Greek world.)

(Simplicius of Cilicia (late 4th to mid 5th century CE) was one of the last Neoplatonists. The details of his connection to the Presocratics are complicated, but the primary points are these. The Neoplatonists part thought of themselves as recovering the true philosophy that Plato had been the last to see most clearly. The object was philosophical truth, not historical fact. To understand Aristotle, who was strongly influenced by Plato, but who also criticized Plato, the Neoplatonists settled for a middle ground that allowed them to treat Aristotle as an authority on logic and physics, but not on the higher realms of reality. Simplicius, in discussing Aristotle, quotes some of the Presocratic philosophers Aristotle discusses. For these quotations, Simplicius seems to rely on summaries in Theophrastus' work on the Presocratics. (Theophrastus (late 4th to late 3rd century BCE) succeeded Aristotle as head of the Lyceum, the school Aristotle founded in 335 BCE.) Theophrastus' work has almost been entirely lost, but Theophrastus' discussions of the Presocratics were summarized by Alexander of Aphrodisias. (Alexander of Aphrodisias (second to third century CE) was an Aristotelian commentator who aimed to articulate and defend Aristotle's philosophy.) These summaries too have been lost, but some extracts are preserved in Simplicius' commentaries on Aristotle's work. The Neoplatonists knew and consulted Alexander's work in their attempt to incorporate Aristotle's philosophy into their reconstruction of the true philosophy Plato had been the last to glimpse.)

The causes in the explanations of things

In the ancient Greek world, "natural" events that unfold in a regular way were traditionally understood in terms of the intentional activity of a mind or intellect. (Rain, for example, is a manifestation of the mind of Zeus. He wills that it rains. This happens in connection with the seasons and the life plants and animals, with occasional severe storms or droughts when Zeus is angry or in certain moods.) The Milesian inquirers into nature challenged this traditional understanding of regularity. This was important. It allowed for the development of science as knowledge about "nature."

The Ancient Greek Philosophical Tradition

The inquiry into nature came into existence in response to a need for an understanding of the world that was more secure than the ones provided in the mythological traditions, and the ancient Greek philosophical tradition in turn emerged out of the need to understand the new insight into reality the inquirers into nature seemed to possess. To understand this new inquiry, people with a certain turn of mind began to ask epistemological and ontological questions. (The Presocratics who asked these questions did not use the noun φιλοσοφία (which is often translated into English as 'philosophy') to describe the enterprise in which they were engaged. This word and its cognates do not become common in the extant literature until the time of Socrates and Plato (5th to 4th century BCE).)

Given the understanding of philosophy as an academic discipline, it is unclear just when this ancient Greek philosophical tradition emerged. It is traditional say that "philosophy begins with Thales and the Milesian inquirers" and that they are the "first philosophers," but the questions they asked and tried to answer seem to belong more to the discipline of physics than to that of philosophy.

Perseus Digital Library:

Hesiod's Theogony, Works and Days

Henry George Liddell, Robert Scott, A Greek-English Lexicon:
ἀρχή, archē, noun, "beginning,"
θεόλογος, theologos, noun, "one who discourses about the gods,"
ἱστορία, historia, noun, "inquiry,"
φιλοσοφία, philosophia, noun, "love of wisdom," (Cicero, On Duties II.5),
φυσικός, physikos, adjective, "natural,"
φυσιόλογος, physiologos, noun, "one who discourses about nature,"
φύσις, physis, noun, "nature"
αἰτία, aitia, noun, "responsibility,"
αἴτιος, aitios, adjective, "responsible"

Charlton T. Lewis, Charles Short, A Latin Dictionary:
natura, noun, "nature"
principium, noun, "a beginning"

Arizona State University Library:
Loeb Classical Library:
Theogony, Works and Days
Early Greek Philosophy, Volume II: Beginnings and Early Ionian Thinkers, Part 1
Cicero, On Duties

The word ἱστορία was the traditional term for investigation that aims for understanding. It transliterates as history and eventually became restricted to historical investigations. This is due in part to the influence of the Histories of Herodotus (484-425 BCE). Herodotus describes the content of his Histories as the result of an "inquiry." In the opening sentence, he writes that "[t]his is the display of the inquiry (ἱστορίης) of Herodotus of Halicarnassus, so that things done by man not be forgotten in time, and that great and marvelous deeds, some displayed by the Hellenes, some by the barbarians, not lose their glory, including among others what was the cause (αἰτίην) of their waging war on each other."

Plato has Socrates says that in his youth he was interested in the inquiry into nature. "When I was young, Cebes, I was tremendously eager for the kind of wisdom which they call inquiry about nature (περὶ φύσεως ἱστορίαν)" (Plato, Phaedo 96a).