The Chronology of the Early Greek Natural Philosophers re-assesses the vital dates of all known pre-Aristotelian Greek natural philosophers, from Thales and Pherecydes to Archytas and Heraclides, thirty-nine in total, and, to the extent the evidence allows, gives compelling and often striking reconstructions of earlier (ancient and modern) judgments about such dates.
Philip Thibodeau has thus written a serious, informed, comprehensive, clever, engaging, and usable book. (It is also free, available via a website of the author’s.) In my own work I am already citing it wherever I make prosopographical claims that fall within its ambit. The book is more broadly valuable than even that, however. It clarifies the decisions that have been made – and must continue to be made – in establishing vital dates that depend on incomplete or inconsistent evidence. It provides a more reliable basis for making claims about synchrony of thinkers than heretofore available, for example of Heraclitus with those others with whom he presents himself in competition (B40 DK). It tells key pieces of the story of ancient and modern biographical chronology – the former with figures like Apollodorus of Athens and Sosicrates; the latter with Diels and Jacoby – that proves an intellectual satisfying historiographical study in its own right. And by re-dating several philosophers, notably the placing of Anaximander and Anaximenes in the mid-sixth and early fifth centuries, it prompts new reflections on the sociology of knowledge: in particular, what difference does it make if much early innovation only started after, say, 530 BCE? Thibodeau does not grandiloquize about this last issue, keeping to the relatively confined desiderata of chronography, but the hints are there – he believes Persian-Ionian interactions in the subsequent decades matter a lot (pp. 7-8). (Another important re-dating is of the death of Pythagoras, to 472.)
Is the book definitive? Well, it is quite complete and pretty transparent. It is hard to gainsay his judgments except from fealty to tradition, a tradition he sharply anatomizes. His results are frequently and openly inconclusive, given inadequacies of the evidence base – take for example Hippo of Samos, with life events datable only to around 440-30 – but just as frequently he makes educated guesses that do appear to follow the better evidence. More might have been said, for example, about the trustworthiness of early Hellenistic authors’ assertions of teacher-student relationships; Thibodeau’s sense is that we should accept them in the absence of substantive and near-contemporaneous reasons not to; while this is interpretatively reasonable, it might take a richer understanding of the circulation of intellectuals in the pre-Socratic period, the circulation of oral lore about that human circulation, and the strength of the Greek desire to find successions within human culture, to feel wholly committed to Thibodeau’s trust in the evidence. Still: it is hard to see how another book could do the same work better.
The book has two main parts. The first seventy pages review the ways that the dates of ancient philosophers have been established for the classical and later Hellenistic periods, and also for the Renaissance humanists and subsequent modern scholars. The next 270 pages proceed one by one through the thirty-nine natural philosophers, for each one starting with translations of all relevant testimonia (or fragmenta) relevant to dating, set in chronological order, then assessing, especially when contradictory, the evidence for and plausibility of each testimonium. Each entry, some a dozen or more pages long, ends with a convenient list of “estimated objective dates.”
So much for the nature and value of The Chronology of the Early Greek Natural Philosophers. One could go on to cite dozens of fascinating and insightful observations; I encourage those working on philosophers discussed in this book to turn to the relevant section – even if much turns out to be familiar, Thibodeau draws out many new connections. In what follows I make four observations.
1. Most of Thibodeau’s dates are not particularly radical, but two are: those of Anaximander and Anaximenes (pp. 227-61). The entry in the Oxford Classical Dictionary (4th ed., 2012) on the elder, written by Charles H. Kahn, has a date of death “soon after 547 BC”; the entry on the latter, by the same author, cites a “traditional floruit 546-525 BC.” Thibodeau argues, by contrast, that Anaximander was born in the 560s and was acquainted with Parmenides and Empedocles into the 480s; Anaximenes was born in the 520s, visits or teaches Parmenides, Anaxagoras, and Diogenes, and is alive to comment on a Spartan earthquake after 465. Thus he down-dates both by half a century.
The earliest explicit testimonia to the vital periods of Anaximander and Anaximenes come from Theophrastus, who in effect claims a direct teacher-student lineage from Thales to Anaximander to Anaximenes to Anaxagoras. But Olympic dating, from authors later than Apollodorus of Athens, puts Anaximander’s 64th year in 547. This is inconsistent with Theophrastus’ view, since it makes nearly impossible a personal relationship between Anaximenes and Anaxagoras (b. 500); it also requires textual emendation of various ancient sources. Subsequent scholars, given its sheen of precision, have generally preferred the Olympic dating – which comes from the late-Hellenistic or post-Hellenistic period, over the much vaguer dating from a source several hundred years earlier. And yet, Thibodeau says, it is hard to imagine that the later historians had so much more or better evidence than those from the 4th century did; and errors may be introduced into precise claims more easily than into vaguer ones. So Thibodeau revisits the pre-Apollodoran evidence, which is extensive and mutually corroborating, in support of his Theophrastus-compatible dates.
But Thibodeau wonders: how did Anaximander’s 64th year get linked with 547 – or rather with the Olympic date equivalent? Long story short, Apollodorus synchronized that age with a sack of Sardis, and a later author placed replaced the sack-synchrony, assuming it to refer to the one involving the Persians, with the equivalent Olympic date. But as Thibodeau points out, there was another sack of Sardis, in 499, this time not by the Persians but by Ionians (Hdt. 5.100), a sack appealed to for synchronizing purposes in other chronological accounts (DL 2.3; Suda ξ.9). If it can be assumed that the converter of Apollodoran synchronies into Olympic dates made a mistake – a simpler mistake to explain, Thibodeau reasons, than the number of mistakes that must be attributed to Theophrastus, Sotion, Diodorus of Ephesus, Diogenes Laertius, and those who said that Pherecydes wrote the first work of Greek prose, none of whom represent Apollodorus as being in late middle age by the mid-sixth century – then a great range of evidence becomes consistent. A similar story may be told about Anaximenes’ case.
One question that Thibodeau does not directly address concerns the position of the accounts of Anaximander and Anaximenes in Apollodorus’ poem in his Chronicle. This work, from the second half of second century BC, deployed synchronisms and, where possible, archon dates. In Thibodeau’s defense, the evidence for the Chronicle’s structure is very scanty, with few direct quotations. Still, for the converter from synchronism to Olympic date to have mistaken one Sardis sack for another half a century earlier, the lines about Anaximander must not have been surrounded by adequately informative context that could establish the relevant half-century; or there was sufficient context but the convertor did not understand it or ignored it; or the convertor was not working directly from the poem but only from an extract (which is likely enough). It would be nice to know what could be said about this.
I note in passing that Thibodeau’s rigorous and open-minded approach to dating on the basis of a full appraisal of the evidence puts new light on the comparatively restricted approach of André Laks and Glenn W. Most in their Early Greek Philosophy. In the introduction to Anaximander, for instance, Laks and Most say that “the ancient sources situate the maturity of Anaximander of Miletus a little before the middle of the sixth century” (vol. 2, p. 271). In the “Chronology” section itself, they include only three passages: Ps.-Hippolytus, Ref. 1.6.7, Diogenes Laertius 2.2, and Pliny, NH 2.31. Thibodeau, by contrast, has thirteen passages. And we learn to see that the Laks-Most passages are only those that rely on precise (and thus accurate-seeming) Olympic dates; these thus post-date Apollodorus and hang on the weak link of an anonymous converter of Apollodorus’ non-Olympic dating to Olympic dating; but without their collocation with the pre-Apollodoran evidence, it becomes difficult to assess their reliability. Trying to get the life-dates of these two early Milesians right is not merely a prosopographical nicety; it helps us understand with whom they were talking. For Anaximenes and his putative monism, an overlap with Xenophanes and access to Parmenides becomes a vibrant possibility, even likelihood.
2. One conceptual creation of Thibodeau’s work is the so-called “Xenophanes gap.” The best evidence has it that Xenophanes went into exile, around age 25, sometime after the submission of Colophon circa 545 by Harpagus, Cyrus’ Median general. This view is accepted by, e.g., Kahn in OCD4 and Laks-Most (vol. 3, p. 3). But that date, which become a notable event for synchronizing Xenophanes’ life with that of his contemporaries, was at some point after Apollodorus but before Diogenes Laertius mistaken for his “prime” age – for his being age 40. Thus his date of birth was pushed back by 15 years (pp. 102-6; less clearly at 14-18). This had a ramifying effect on the dating of his contemporaries, which in later sources show systematic back-shifts of 15 years from what earlier evidence would suggest (pp. 69-70). Thibodeau has identified the source of those errors.
3. Thibodeau provides a reading of the fragment from Alcidamas’ On Nature that makes it plausible (from DL 8.56, my translation):
Alcidamas, in the Physics, says that Zeno and Empedocles ἀκοῦσαι Parmenides at the same time, that later they separated from him, and that, whereas Zeno philosophized on his own, the other continued on to διακοῦσαιAnaxagoras and Pythagoras, emulating the latter in his dignity of life and bearing, and the former in his physical investigations.
Alcidamas could be right, Thibodeau says, because Empedocles (born around 496) could in fact have studied with Pythagoras (died in 472; see pp. 107-46, a fascinating essay on its own), Anaxagoras (born around 500; see pp. 166-77, much more efficient than Jaap Mansfeld’s two-part article on the subject), and Parmenides (born around 520; see pp. 152-8); this statement also gives independent support for these dates (established by appeal to non-Alcidaman sources). As Thibodeau writes, in an expression of his “oldest-first approach” to dating: “This report has often been dismissed due to its chronological implications, yet Alcidamas, who was about a decade older than Plato, is one of our oldest sources; he was also an intellectual ‘grandson’ of Empedocles, since his own teacher Gorgias had studied with the philosopher-poet” (p. 122). It would be more convincing, however, to have had a justification for taking ἀκοῦσαι and διακοῦσαι literally and not merely as “studied [the works of]” and, as I mentioned above, a credible picture of oral transmission of facts about pedagogical interaction.
4. I would have appreciated – because I appreciated so much else about the book – the inclusion of entries on Gorgias and Protagoras, even if, as Thibodeau claims, they “only touched on the exact and natural sciences at the margins” (p. 4 n. 3); after all, both were important members of the milieu represented by Xenophanes, Parmenides, Melissus, and Zeno, with work and ideas in conversation with that of those authors. And Antiphon is included. Socrates, who has uncontroversial dates of birth, military action, and death is not included, although there are enough relevant controversies to have made it worthwhile: his putative interaction with Archelaus, including the trip with him to Samos reported by Ion of Chios, perhaps to visit Melissus, and the natural philosophizing activities attributed to him by Old Comic authors and perhaps by Plato. And about the entry on Plato: it rightly remarks on the controversy about his date of birth (somewhere in the 420s), the issue depending on his age at the start of the Thirty and in the last years of Socrates’ life; but I would have appreciated a closer study of the Seventh Letter, in particular the language at the opening of the passage about Thirty – Νέος ἐγώ ποτε ὢν πολλοῖς δὴ ταὐτὸν ἔπαθον· ᾠήθην, εἰ θᾶττον ἐμαυτοῦ γενοίμην κύριος, ἐπὶ τὰ κοινὰ τῆς πόλεως εὐθὺς ἰέναι (“When I was young I felt as many others do: I thought, on my soon becoming master of myself, that I would right away enter public life,” 324b–c).
 Thibodeau deals with these authors in three groups: those we know to have been dealt with by Apollodorus except for two; Anaximander and Anaximenes as special cases of those who were dealt with by Apollodorus; and those we do not know to have been dealt with by Apollodorus. Group 1: Thales of Miletus, Pherecydes the Syrian, Xenophanes of Colophon, Pythagoras of Samos , Heraclitus of Ephesus, Parmenides of Elea, Zeno of Elea, Melissus of Samos, Anaxagoras of Clazomenae, Empedocles of Acragas, Democritus of Abdera, Plato of Athens, Theaetetus of Athens, Eudoxus of Cnidus. Group 2: Anaximander of Miletus, Anaximenes of Miletus. Group 3: Democedes of Croton, Lasus of Hermione, Cleostratus of Tenedos, Hecataeus of Miletus, Scylax of Caryanda, Alcmaeon of Croton, Hippasus of Sybaris, Leucippus of Miletus/Abdera, Oenopides of Chios, Archelaus of Athens, Diogenes of Apollonia, Hippo of Samos, Antiphon of Athens, Philolaus of Tarentum, Eurytus of Tarentum, Theodorus of Cyrene, Hippocrates of Chios, Meton of Athens, Euctemon of Athens, Ecphantus of Croton, Metrodorus of Chios, Archytas of Tarentum, Heraclides of Pontus
 The book is self-published, currently the only work by Cosmographia.net. The author-publisher says that the book has been “open” peer-reviewed, though he does not claim that review to have been high-stakes, only that “feedback [has been] taken into account in the usual way,” whatever that might mean. The copy-editing and proofreading have been done to a good level; I noted no more typos than I am familiar seeing in books from autonomous publishers.
 I leave to the footnote, as being outside the scope of this book itself, that Thibodeau’s mission for Cosmographia.net is at least to publish eight more books that have the burden to show that “Greek natural philosophers revised lore and ideas from neighboring cultures to a much greater degree than has hitherto been acknowledged. Recognizing this borrowing in turn allows us to perceive more clearly the original contributions of the Hellenic thinkers, who were particularly interested in paradoxes, cycles, visual representations, and questions about causality and substance” (quoting from the Q&A page of the website). Whatever the success of the enterprise, which looks promising, it is exciting to anticipate such a wholesale confrontation with ancient Greek philosophy.
 That Apollodorus did not use Olympic dates Thibodeau says is “widely accepted” (p. 36; cf. 34), but he fails to give the reasons for believing it, and the nine illustrative quotations of Apollodorus cited on pp. 34-5 all contain Olympic dates. For the reasons, see BNJ 224 (publ. 2018), “Biographical Essay,” with references.