In defense of the PACE trial, Petrie and Weinman employ a series of misleading or fallacious argumentation techniques, including circularity, blaming the victim, bait and switch, non-sequitur, setting up a straw person, guilt by association, red herring, and the parade of horribles. These are described and explained.

Petrie and Weinman (2017) devote fewer than three pages to their defense of the PACE trial, but they nonetheless manage to employ a virtual catalog of misleading or fallacious argumentation techniques. These include circularity, blaming the victim, bait and switch, non-sequitur, setting up a straw person, guilt by association, red herring, and the parade of horribles. Sometimes they engage multiple fallacies in a single paragraph, as I shall explain seriatim.

Circularity A circular argument assumes or incorporates the desired answer in the premise of the question itself. Petrie and Weinman engage in circular reasoning when they begin with the statement that “differing beliefs about the causes of chronic fatigue syndrome (CFS) still influence how scientific studies in this area are accepted and evaluated.” They offer no proof for this assertion, although they revert to it repeatedly throughout the paper, claiming, for example, that “this is really the key issue behind the criticisms of the PACE study” and “causal beliefs are an important factor in the way patients understand their illness” (citing only themselves for the latter proposition). As with any study, the PACE trial can be made self-evidently impressive if one begins by assuming the validity of its conclusions. The very point of contention regarding the PACE trial, however, is whether or not myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) symptoms are the product of patients’ “unhelpful” or “dysfunctional” illness beliefs. This is the longstanding theory of White, Chalder, and Wessely (Wessely et al., 1996, 1989; White et al., 2011), but it has been disputed by many others and it has been flatly rejected in a report by the US Institute of Medicine (IOM (now the Academy of Medicine), 2015). Disagreement is fair play in scholarly discussion, but eliding contrary research is not.

Blaming the victim Petrie and Weinman express puzzlement at patients’ resistance to cognitive behavioral therapy (CBT) and graded exercise therapy (GET), noting that “In our experience as health psychologists, patients with other diseases such as cancer, renal disease, heart disease or chronic respiratory problems are usually very keen to adopt psychological interventions that can reduce fatigue, improve functioning and well-being.” The implication is that there must be something wrong with ME/CFS patients, or some flaw in their belief systems, given their deviation from the behavior of patients with other illnesses. It must be their own fault if ME/CFS patients do not find CBT and GET beneficial, given how much the therapies are appreciated by everyone else. Entirely missing from the discussion is the reason that ME/CFS patients part ways from those with cancer or renal failure. Petrie and Weinman assert that the difference is solely attributable to correctable “beliefs,” while failing to consider that it instead lies in the actual experience of ME/CFS patients.

Bait and switch Continuing the cancer comparison, Petrie and Weinman also inform us that “A recent review of cancer-related fatigue also found that exercise and psychological interventions, and both used in combination, were effective and recommended that clinicians should prescribe exercise and psychological therapy for cancer related fatigue.” This is an example of the bait and switch. The premise of the PACE trial, as Petrie and Weinman never acknowledge, was that ME/CFS is “reversible” through CBT and GET (White et al., 2011). In fact, the PACE investigators claimed that CBT and GET achieved ME/CFS “recovery” rates of 22 per cent (White et al., 2013). No reputable physician would claim that cancer is reversible through exercise and psychotherapy, much less boast about subsequent recovery rates. Thus, the experience of palliating cancer—or renal disease, or heart disease—with psychological interventions has no bearing on ME/CFS or the validity of the PACE trial (Wilshire, et al, 2016).

Non-sequitur “Most diseases are caused and perpetuated by a complex mix of behavioural and physical factors,” explain Petrie and Weinman, “and hence will be best managed by a range of treatments (e.g. lifestyle change, self-management and medication).” This statement is either trivial, in that all illnesses may benefit from a range of treatments, or a non-sequitur, in that it treats physical causation and behavioral perpetuation as though they are comparable when, in fact, they are often distinct phenomena. There is no doubt, for example, that the disability of a broken leg may be “perpetuated” by sub-optimal behavior and poor self-management, but that does not tell us anything about the underlying physical nature of the injury. In other words, the jump from perpetuation to causation is a non-sequitur.

Straw person “The use of exercise when someone feels fatigued is counterintuitive to the common sense model of CFS,” say Petrie and Weinman, suggesting that patient objections to GET are merely intuitive or perhaps even a “modern-day version of Cartesian dualism and a rather crude division between mind and body.” Here, they are wrestling with a straw person, as they are setting up arguments—none of which have ever been made—solely for the purpose of refuting them. Critics of the PACE trial do not rely on intuition and do not indulge Cartesian dualism either crudely or otherwise. Rather, patients report having attempted exercise only to experience devastating relapses or crashes (Brea, 2017; Tuller, 2016). Although one would not know it from the Petrie and Weinman paper, the US Institute of Medicine (now the Academy of Medicine) has concluded that exertion intolerance is the defining characteristic of ME/CFS and has even proposed changing the name of the illness to Systemic Exertion Intolerance Disease (Institute of Medicine, 2015). Needless to say, the IOM report was not based on intuition or mind-body dualism.

Guilt by association The JHP special section on ME/CFS was initiated by Geraghty’s (2016) very measured and thoughtful paper detailing the documented shortcomings of the PACE trial. Nonetheless, Petrie and Weinman seek to tarnish his (and others’) criticism by invoking attacks on “the researchers themselves” and bemoaning the “intimidation of researchers in the CFS field.” Geraghty and other PACE critics—such as the contributors to this special section—have neither attacked nor intimidated anyone. Although such deplorable behavior has evidently occurred (which I will address in the next section), it cannot be attributed to serious academic and professional critics of the PACE trial, who now number over 100 (Ablashi et al., 2017), and there is no point in bringing it up other than to impute guilt by association.

Red herring In any case, the story of researcher intimidation is a red herring—an argument that serves only as a distraction from a relevant or important issue. In support of their claim, Petrie and Weinman cite two reports from 2011, both of which detail complaints of harassment by PACE and other ME/CFS researchers. I understand from other sources and private correspondence that certain ME/CFS researchers have been on the receiving end of extremely disturbing phone calls and emails, although not within the past several years. There is no excuse for such behavior, which must be condemned by all concerned. But what could be the point of raising it in a response to Geraghty’s critique of PACE, which is completely unrelated to any sort of threats or provocations? Moreover, Petrie and Weinman do not tell us that the broadest allegations of harassment were rejected in a 2016 judicial ruling that ordered the PACE team to disclose their underlying research results pursuant to a Freedom of Information request. The First Tier Tribunal (2016) found that the stories of threats against the PACE investigators were “grossly exaggerated and the only actual evidence was that an individual at a seminar had heckled” one of them. Overstated reports of years-old events are a classic red herring that does nothing other than divert attention from serious criticism.

Conclusion Petrie and Weinman are deeply committed to their “belief-driven” theory illness and recovery. Although not mentioned in their paper, Petrie and Weinman appear to be the only two members of the “health advisory team” of a company called Atlantic Healthcare, which promotes a “Belief-driven Behavior Change approach” that is marketed to “healthcare providers, public health systems, insurers and pharmaceutical companies.” According to its website, the company works with “insurers to improve health and wellbeing and reduce the cost of care” (Atlantis Healthcare, 2017). While I do not question the sincerity of Petrie and Weinman’s faith in their theory, and it is not unusual for academics to consult with industry, the relationship with Atlantis Healthcare is relevant to their paper and should have been included in their declaration of conflicting interests.

Declaration of conflicting interests

The author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: He was diagnosed with myalgic encephalomyelitis /chronic fatigue syndrome (ME/CFS) in 2006. Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.