A mighty wind

To the Editor:

De Boer et al. offer a suggestive, but not substantive, reply to our critical examination of their widely reported claim that ethylene intoxication was a probable cause of the mantic states of the Pythia at the Delphic Oracle. Their reply is inadequate for a number of reasons. The main problem is that de Boer et al. appear to have misunderstood our argument. They claim that our article reasserts “the orthodox position of 20th century classical scholars” that “there is no truth to the ancient tradition of unusual geological phenomena at the oracle site.” Even a cursory reading of our article shows that this is not our criticism of the de Boer team's argument.

Our criticism is that their argument included a number of implicit premises and claims with neither empirical nor logical support. In our article, we identify two major problems with their argument. The first problem is that the de Boer team has not demonstrated that gaseous hydrocarbons (GHCs) were present at the ancient Oracle site at Delphi in sufficient quantities to cause intoxication of the Pythia. We acknowledge the possibility that in the dimmed adyton, the rate of ethylene decay may have been less than in sunlight. But, we re-iterate the basic point of our original argument, which is that the de Boer team offers two claims that necessarily make their hypothesis an untestable speculation: (a) in the past, ethylene accumulated in the adyton in sufficient quantities to cause the intoxication of the Pythia, but (b) ethylene is now undetectable because of its (non-photochemical) decomposition in the travertine rock. The second problem we identify is that the de Boer team assembled spurious evidence and a fallacious argument to suggest that the mantic behavior of the Pythia resembled the behavior of an individual intoxicated with ethylene. Even from this précis, it should be clear that we are entirely neutral on the question of whether there was unusual geological phenomena at the Oracle site. Hence, we continue to reject the de Boer team's argument for connecting ethylene intoxication with mantic behaviors. This argument has also been rejected by Etiope et al. (1).

In their letter, the de Boer team offers several broad accusations. Given a clear understanding of our original argument, and Etiope et al.'s rejection of the ethylene intoxication hypothesis, only two accusations are germane to the present discussion, namely, the assertion that we misunderstand the classical sources and the assertion that we misunderstand the scientific method. Let us carefully examine these charges.

The de Boer team implies that Etiope et al. confirms their basic argument but instead of ethylene “suggest that benzene was the sweet smelling gas that triggered the oracular trance.” However, this is not a straight-forward reading of the conclusion offered by Etiope et al. Although Etiope et al. admit the possibility of the “basic hypothesis of hydrocarbon emissions,” they also conclude that “the possibility of significant ethylene emissions is not obvious.” This empirical claim is in agreement with our logical analysis. Furthermore, like us, Etiope et al. are cautious about the GHC intoxication hypothesis in toto. The Etiope team observes that the mere possibility of a GHC intoxication hypothesis does not suggest that it is likely or probable. Etiope et al. carefully state: “If any gas-linked neurotoxic effect of Pythia needs to be invoked, as suggested by historical tradition, it could be searched for in the possibility of oxygen depletion due to CO₂–CH₄ … ” (our emphasis). They continue: “Should archaeologists require a reason for the natural presences of sweet odours, an alternative geological explanation could be the occurrence of aromatic hydrocarbons, such as benzene, dissolved in the groundwater spring” (our emphasis). From this conclusion, it is clear that Etiope et al. endorse some variety of the GHC intoxication hypothesis only on the grounds of the particular interpretation of the historical evidence promoted by the de Boer team, an interpretation which we argue is confused.

In their original article, de Boer et al. assert that “ancient historical references consistently describe an intoxicating gas, produced by a cavern in the ground, as the source of the power of the oracle at Delphi”(2). In their letter, de Boer et al. offer a restricted version of this claim that emphasizes the importance of the testimony of Plutarch: “Throughout his writings Plutarch makes it clear that the oracle's power was believed to derive from a physical, geological source.” They again underline the importance of Plutarch's testimony in the conclusion to their letter: “the burden of proof now rests with the detractors of Plutarch and the other sources … ”. In our article, we point out that ancient sources, including Plutarch, do not offer a description of the Delphic Oracle consistent with the de Boer account. Of the historical sources they cite, not one of them – not one – states all of the following: that there is (a) a chasm, fissure, or cavern that produced (b) a detectable gas, which was (c) intoxicating and which (d) was the source of power of the Oracle. Some sources say one thing, others another. There are, as we showed in our article, serious problems with attributing the crucial claim (c) to any of the ancient sources. With respect to Plutarch's testimony, Plutarch may be saying something like (b), but not (a) or (c), and he equivocates on (d). Even for what Plutarch says that might lead us to think (b), we cannot accept his testimony without some serious qualifications. These qualifications necessarily arise from an appreciation of the technical problems in appraising and interpreting ancient sources. The de Boer team's interpretation of the ancient sources in general, and Plutarch in particular, faces unsurmountable technical difficulties.

Unfortunately, the de Boer team gathers their evidence from Babbitt's imprecise and colloquial 1936 translation of Plutarch. Unfamiliarity with the original Greek text, and the philosophical context in which Plutarch was writing, leads de Boer et al. to assume that terms translated by Babbitt as “exhalations”, “airs”, “breaths”, and “spirits” must refer to what we would now call gases. Plutarch's use of the term (def. Or. 432D10) considered in isolation might lead a reader to this interpretation. However, in the context of Hellenistic physics, the term is offered as an explanation of a wide range of phenomena including winds, volcanoes, the formation of metals in the earth, the cohesion of solid bodies, foetal development, and consciousness. The de Boer team misses the fact that when Plutarch says that divination is aided by a certain he is not referring to a gas that he has detected but to an imperceptible substance that fills the universe, holds it together, and causes the appearance of action at a distance. As A.A. Long explains, is a specific, technical term that means, for at least one Hellenistic school, “the divine ‘active principle’ of the world in its entirety” (3). To take a parallel medical example, in Plutarch's time, the arterial system, the eyes, and the nerves were said to be filled with We cannot reason from this claim to the conclusion that a gas was observed blowing out of punctured arteries or severed nerves. On observing the function of the nerves, eyes, and arteries, the ancient scientists reasoned (incorrectly but interestingly) that there must be an underlying cause in the form of an imperceptible substance, which they called

Furthermore, even when ancient sources appear to use more concrete terms in connection with Delphi – for instance, – caution is still required as this term is often used when a causal agent is unknown or cannot be detected. For example, Plutarch cites Hesiod to claim that the demigods are made of (4), whereas medical sources claim that are the cause of epidemic diseases. We would be rash to infer from the latter claim that any concrete and causally efficacious difference in air quality had been detected by ancient physicians at the outsets of epidemics. In short, the meanings of and related terms are a long way from our mundane gas, wind, or breath.

De Boer et al. further assert that Plutarch testifies that there was a sweet smell emitted in the oracular chamber and that Plutarch suggested that the intensity of the emission had been diminished by geological phenomena. The de Boer team glosses over the fact that Plutarch's text is a dialogue in which the theory is advanced not by Plutarch-the-eye-witness-at-Delphi but by a semi-fictional character named Lamprias. In the dialogue, Lamprias offers reports of natural phenomena at the Delphic Oracle to advance the argument that divination is a physical phenomenon and therefore is a legitimate science. Lamprias' specific interest and motivation means that testimony offered in his voice needs to be handled with circumspection. There are several reasons for this. (a) Lamprias stands as the representative of a particular philosophical school and his opinions about the Oracle are always meant to be biased in a particular direction. (b) He is not an eye-witness (we know from a separate dialogue that he is expressly contrasted with “those associated with the temple”). (c) Claims Lamprias has made about the Oracle are known to have contradicted, possibly to the point of angering those who actually lived in and worked at Delphi. And, perhaps most crucially, (d) he is accused by an interlocutor on at least one occasion of deliberately falsifying data, “changing data and reports” to suit his argument.

De Boer et al. wish to link Lamprias' report of a sweet smell to the presence of aromatic hydrocarbons. But again, Babbitt's translation leads the team astray, for Babbit has unfortunately (and incorrectly) added the phrase “it is a fact that … ” to Lamprias' description of the odor. The Greek text has no such preface. On the contrary, the text shows that Lamprias is all too conscious that he has a reputation as a teller of tall tales and that he is aware that his audience will think he is merely speculating. He concedes that his story may seem implausible to his audience: Lamprias ends the dialogue by conceding to his interlocutors that even he is unsure of how secure his story has been, including his report of the sweet-smelling gas. He states that he will have to think more about it, for his account has been speculative and provocative, “such that there are many objections and suspicions that contradict it.”

In their letter, de Boer et al. claim that “Foster and Lehoux also misunderstand the process of standard scientific method, which starts with a hypothesis and then tests the hypothesis against data.” They then offer the problematic claim that “the hypothesis is not accepted unless it is confirmed by the evidence.” The account of the scientific method offered by de Boer et al. depends on the idea of empirical evidence confirming hypotheses. This account runs into a number of difficulties, including Hume's notorious problem of induction and Hempel's famous black-raven paradox. Most scientists with whom we have collaborated, recognizing these problems, are methodological Popperians. According to Sir Karl Popper, the logic of scientific discovery is a logic of conjecture and refutation(5). That is, following Popper, scientific hypotheses undergo a process of falsification – not confirmation. A hypothesis may be falsified by either of two procedures: (a) it may be shown by experiment or empirical evidence to be false or (b) it may be shown to be false by logical analysis. In our article, we adopt procedure (b).

In our article, we level the charge of logical circularity against a particular claim made in the de Boer team's original argument, not against their overall method. The circular reasoning occurs in de Boer et al.'s argument arising from their table 1, which parallels descriptions of the Pythia in a normal mantic session with descriptions of mild anesthesia with “ethylene or nitrous oxide.” Their table includes this logical circularity: the mantic behavior of the Pythia is only attributable to ethylene intoxication, if it is first assumed that ethylene intoxication is the cause of the Pythia's mantic behavior. Without that assumption, any number of causes other than ethylene intoxication might explain the behavior of the Pythia. (Indeed, individuals in modern religious groups sometimes exhibit mantic behavior during ritual without the presence of GHCs or other intoxicants.) In other words, the logical problem is that the argument has its conclusion as one of its premises. As the scientific method is, at core, a logical method, a logical fallacy in de Boer et al.'s argument means that the method has not been followed rigorously.

In their letter, de Boer et al. concede that, “It is not surprising that ethylene was not detected in the travertine rock around the temple.” They observe that “Ethylene is highly reactive” and go on to argue that “the original ethylene would be chemically altered to form ethane and/or methane, also intoxicating hydrocarbons, which were found in the travertine.” This is an important modification to their original argument. However, the de Boer team now seems to be offering a hypothesis that is not falsifiable. Their revised hypothesis seems to be that some GHC (possibly benzene, ethylene, ethane, and/or methane) was the “probable cause” of the Pythia's mantic states (2). To show this hypothesis, an argument of the following basic form is offered. (a) If there are indications of concentrations of GHCs above atmospheric backgrounds, then the Pythia's mantic states are attributable to intoxication by GHCs. (b) If there are indications of low concentrations of GHCs (relative to atmospheric backgrounds or levels required for intoxication effects), then either geological conditions have changed or GHCs have decomposed or diffused over time, such that GHC concentrations were higher in the past than at present. And so, the Pythia's mantic states are still attributable to intoxication by GHCs. (c) Therefore, if GHC concentrations are relatively high then the Pythia was intoxicated, or if GHCs are relatively low then the Pythia was intoxicated. The de Boer team wishes to claim that this form of reasoning is scientific hypothesis testing. However, given the form of their argument, there is no possibility of falsifying the hypothesis. Recall that, following Popper, it is the possibility of falsification that distinguishes genuine scientific hypotheses from their pseudo-scientific counterfeits.