Critics and advocates alike have expended much effort defining Evidence-Based Medicine. However, there has been little consensus about what “Evidence-Based Medicine” is. Some authors see ‘EBM’ as something one believes—a view about medicine. Others interpret EBM as something one does—a particular way of practicing medicine. Still others seem to view EBM as an identity for clinicians, something one is—‘I am an evidence-based practitioner’. EBM is sometimes a diagnosis of exclusion: EBM is defined by what it rejects, namely reliance upon clinical experience, expertise and biological theorising in medical practice. This approach was prominently taken in the 1992 article by the EBM Working Group which launched the term ‘Evidence-Based Medicine’. There are kernels of truth to these characterisations, but none are individually satisfactory. Rather, I characterise of EBM as a movement within medicine.
Before defending this ‘movement’ interpretation of EBM, we should review the existing attempts to define EBM, especially those of prominent EBM advocates. I identify four types of definition of EBM, which I call the ‘Four Ps’: Platitude, Paradigm, Principles and Process.
The Four Ps
Perhaps the most commonplace ‘definition’ of EBM is a platitude which originates with David Sackett . This platitude appears on covers of EBM books, and is regularly quoted in its entirety in articles and on web-sites by proponents and critics of EBM alike.
EBM Platitude: “Evidence based medicine is the conscientious, explicit, and judicious use of current best evidence in making decisions about the care of individual patients.”
This ‘definition’ has been rightly criticised as empty and uninformative. It entirely fails to distinguish EBM from its predecessors and alternatives. As Worrall has observed, surely medicine was always based on evidence. Moreover, opponents of EBM clearly agree entirely with basing medical decision-making upon the current best evidence, but merely disagree with EBM understandings of “best”. The debate, then, is about the interpretation given to ‘best’ (and sometimes ‘evidence’).
Similar, less prominent platitudinous definitions abound. Variations include Gordon Guyatt’s “the application of scientific method in determining the optimal management of the individual patient”.  Daly reports Guyatt’s updated definition as: “Evidence-based medicine is an approach to practicing medicine in which the clinician is aware of the evidence in support of her clinical practice, and the strength of that evidence”.  These definitions all suffer the same problems—they are uninformative and fail to distinguish EBM from its counterparts.
The ‘Paradigm’ definition of EBM conceptualises ‘Evidence-Based Medicine’ as a Kuhnian paradigm for clinical practice. Unfortunately, the term ‘paradigm’ suffers from radical ambiguity. However, the features commonly expected of a paradigm include: a set of foundational assumptions agreed upon by all within the discipline; a way of viewing the content of the discipline and the problems it can and cannot solve; and, the methods which are and are not appropriate for use in solving those problems.
The Paradigm definition is particularly influential within the EBM literature because it was prominently used in the EBM Working Group’s 1992 article which unveiled EBM to the world. The Working Group proposed a ‘paradigm shift’ in medical practice. The focus upon the shift, however, introduces another definitional ambiguity: we must ask whether “EBM” refers to the new paradigm, or to the paradigm shift itself. Is ‘EBM’ supposed to be a theoretical framework like Newtonian mechanics, or an historical event like the Copernican Revolution? Both interpretations are expressed in the surrounding literature.
What has become clear, however, is that early EBM proponents did not intend to endorse a Kuhnian philosophy of science, or even to claim that medical practice undergoes Kuhnian revolutions—periods of ‘normal science’ interrupted by paradigm shifts due (in large part) to the accumulation of anomalies. It is more likely that the term ‘paradigm shift’ was being used in a colloquial sense to indicate a major change of ideology or practice. A number of prominent EBM proponents subsequently dissociated from the term ‘paradigm’, and some have acknowledged that it was used unreflectively. Critics have addressed the problems of whether clinical practice can be aptly described as paradigm-based, whether Kuhnian history applies to medical practice, and whether the transition to EBM can be described as a Kuhnian paradigm shift. I will not recapitulate their arguments here. At best, a convoluted interpretation of Kuhn is required to force a fit.
Although paradigm definitions of EBM are now unpopular, they remain relevant as an argumentative refuge. When attempts to explicate precise ideas or practices definitive of EBM fail, the retreat to a looser ‘worldview’ conceptualisation of EBM becomes appealing.
The ‘Principles’ approach to defining EBM consists of providing a set of principles, ideas or assumptions which are shared by EBM proponents. ‘Principles’ approaches conceptualise EBM as something believed, rather than done. Two sets of principles are particularly influential as definitions of EBM. First, the “five linked ideas”, described by both Davidoff et al. and Sackett & Rosenberg:
- that our clinical and other health care decisions should be based on the best patient- and population-based as well as laboratory-based evidence;
- that the problem determines the nature and source of evidence to be sought, rather than our habits, protocols or traditions;
that identifying the best evidence calls for the integration of epidemiological and biostatistical ways of thinking with those derived from pathophysiology and our personal experience;
- that the conclusions of this search and critical appraisal of evidence are worthwhile only if they are translated into actions that affect our patients;
- that we should continuously evaluate our performance in applying these ideas.
Several of these principles are uncontroversial and laudable. (2)’s insistence that tradition is not sufficient justification for reliance upon particular evidence-sources is an accepted assumption in philosophy of medicine, while (5) defends performance evaluation, which (though not always practical) is a worthy ideal. Moreover, while (1)’s claim that laboratory-based evidence is insufficient for healthcare decision-making is controversial, it seems difficult to dispute that using patient- and population-based evidence as well is desirable. (4) is a practical concern definitive of the art of clinical practice, as opposed to scientific research (which may be worthwhile even without practical applications).
Principle (3) is perhaps the controversial heart of the set. Building upon (1)’s claim that laboratory-based evidence is insufficient for healthcare decision-making, (3) calls for the use of epidemiological and biostatistical evidence such as RCTs and observational studies. In Sackett & Rosenberg’s account, the claim seems innocuous. Epidemiological evidence is to be integrated with clinical experience and pathophysiology. However, elsewhere, the EBM movement would denigrate clinical experience and pathophysiology, and subsequently promote subordinating non-epidemiological evidence to epidemiological evidence.
While these five principles illustrate much of EBM’s core ideas (the focus upon practice, the insufficiency of laboratory evidence, the importance of epidemiological and biostatistical evidence), they do not express the mechanics of EBM in practice. They offer no indication as to how different evidence-sources are appraised, integrated or applied.
A second ‘principles’ approach was very prominently defended by Guyatt et al. in the first chapters of the book compilation of the Users’ Guides to the Medical Literature series.  In their chapter entitled The Philosophy of Evidence-Based Medicine, Guyatt et al. summarise EBM through two “fundamental principles”:
“EBM involves 2 fundamental principles. First, EBM posits a hierarchy of evidence to guide clinical decision making. Second, evidence alone is never sufficient to make a clinical decision.”
Here, hierarchies are brought to centre-stage: a hierarchy of evidence guiding clinical decision-making is the foremost principle of EBM. Notably, hierarchies were absent from the five linked ideas. The hierarchy places epidemiological evidence at the top (notably RCTs), with laboratory-based evidence (aka. “Physiologic studies”) and clinical experience at the bottom. The second principle, the insufficiency of evidence, is a concession to the importance of patients’ rights and input: decisions must be made with the patients, rather than about them, and their values and preferences should be taken into account. Notably, no further mention is made of this second “fundamental principle”: the remaining Users’ Guides offer no substantive guidance for the interpretation and integration of patients’ values. By 2002, the hierarchy is clearly the most important, defining feature of EBM for Guyatt et al. Moreover, we should note the abandonment of the notion of “integration” of evidence sources in this account.
I have noted that Principles definitions tend to omit the practicalities of how these ideas are implemented. Just such concerns underpin the final class of EBM definitions offered by the proponents: process definitions.
Process definitions present Evidence-Based Medicine as something done, rather than believed. One is doing Evidence-Based Medicine when one follows a particular procedure. The most influential process definition originates from Rosenberg & Donald, and Sackett & Rosenberg, defining EBM as a four- or five-step process:
- Formulate a clear clinical question from a patient’s problem
- Search the literature for relevant clinical articles
- Evaluate (critically appraise) the evidence for its validity and usefulness
- Implement useful findings in clinical practice
Sackett & Rosenberg’s five-step process adds “evaluating performance” as a fifth step (in common with their fifth principle).  This approach was prominently adopted by the so-called “Bible” of EBM, Sackett et al.’s Evidence-Based Medicine, which is structured into five parts, each devoted to explicating a step in the process:
- Setting the Question
- Finding the Evidence
- Appraising the Evidence
- Applying the Evidence
- Evaluating Performance
As described, ‘doing EBM’ seems little different to traditional medicine. What sets EBM apart is its prescription of which evidence should be found and how that evidence should be appraised. The Users’ Guides and Evidence-Based Medicine give detailed instructions on appraisal. Originally, the Users’ Guides presented checklists of desirable design features. For example, Guyatt, Sackett & Cook’s checklist for evidence has five criteria for “valid” results: randomization, intention-to-treat analysis, blinding, baseline comparability of the groups, and equivalent treatment of the groups in all respects other than the allocated therapy (i.e. absence of treatment bias). Such checklists lay out the ideal study-design. Often, no indication of what to do with other studies is provided. Sometimes, clinicians are advised to simply discard studies which do not meet these standards. 
Subsequently, EBM approaches to critical appraisal became more nuanced with the adoption of hierarchies of evidence. Hierarchies were first introduced into the EBM literature in 1995, though had been a fixture of clinical epidemiology for many years previously. Hierarchies provided a tool for critical appraisal of medical evidence according to study-design. Studies are ranked in terms of the quality of evidence they provide. Hierarchies such as Guyatt et al.’s were crucial to fulfilling Step 3 in the EBM Process.
Hierarchies also gained, by extension, a role in Step 2, finding the evidence. Clinicians have scarce time-resources for consulting research literature. They naturally prefer to locate the highest-quality evidence in Step 2, limiting the time spent evaluating lower-quality evidence. Hence, hierarchies and checklists both play a role in finding evidence—literature searches can be prioritised to detect high-ranking evidence, for example by including the search terms “randomized” or “randomization” in searches. 
Hence, although the five abstract steps of the EBM process could describe most clinicians’ approach to clinical practice, it is the detail of the execution of these steps, particularly steps 2 and 3, which distinguish EBM from its counterparts as a characterisation of clinical care. Hierarchies (and beforehand, checklists) are a crucial part of these distinctive steps, making the EBM process controversial and different from what came before. On this definition, as on the Principles account from Guyatt et al., it is really the hierarchical appraisal mechanism that characterises EBM.
However, defining EBM as a process risks an overly narrow interpretation of Evidence-Based Medicine. EBM proponents have not focused solely upon the process of using evidence in clinical practice. They also defend ideas about medical pedagogy, research and public health. Claiming that EBM is exclusively done by practicing clinicians in their practice limits the scope of EBM’s application in a way which many proponents reject. The process itself does not seem fundamental to Evidence-Based Medicine. Rather, in many presentations, the process is a vehicle to implement the principles or paradigm in practice. To define EBM via the process seems to conflate practical implementation with underlying motivation. Many more recent EBM texts omit the appraisal process entirely in favour of implementing pre-appraised evidence: Cochrane reviews, systematic reviews, meta-analyses and summaries. Clinicians using pre-appraised evidence are still under the umbrella of EBM practitioners, despite following a different process.
Ps in a Pod? Disunity and other definitional strategies.
The explicit attempts at defining EBM are not the only definitional strategies apparent in EBM texts. Perhaps a more complex definition is needed, utilizing two or more of the ‘Four Ps’ in unison.
The simplest strategy is to allow ‘EBM’ to have several meanings. Care must be taken to avoid equivocating between the different senses of EBM, but a single term having multiple meanings is far from unusual.
However, this plurality of meanings of ‘EBM’ is unhelpful here. Suppose we take three or four of the Four Ps as correct meanings of ‘EBM’—EBM is a paradigm, but also a set of principles and a process. This strategy inherits all the problems of the individual definitions. The paradigm definition is still a misused term with implications which are unacceptable to most EBM proponents. There remains no consensus concerning the principles which are defended, or how they should be explicated or applied in practice. The platitude is still empty and fails to differentiate EBM from its counterparts. Finally, performing the EBM process is not a necessary condition for being an EBM practitioner, nor does EBM solely relate to clinical practice. A similar problem applies to the strategy of taking one definition as fundamental and using the others to explicate and clarify it. For instance, one might define EBM as a new paradigm, and explicate that by defining the paradigm in turn as a set of principles and a new process for clinical practice.
A more nuanced approach might go deeper, extracting the common underlying precepts which underpin the Four Ps and the variants upon them. Perhaps the Four Ps are just different attempts to present the same core ideas, which constitute EBM.
What might these core ideas be? One component may be the belief that RCTs provide the best evidence for use in clinical practice, and that randomization is extremely important for the quality of evidence from a trial. Another is that non-biostatistical evidence—whether from clinical experience, laboratory studies, or biological rationale—is unreliable, or at least less reliable than population-based epidemiological studies, for informing clinical practice. Finally, EBM involves a commitment to changing clinical practice to use more RCT evidence and rely less on authority, experience and biophysical reasoning.
However, these core ideas are not jointly sufficient for believing in EBM. Most people in the debate would happily accept that RCTs can be very high-quality and non-epidemiological evidence can be unreliable. Certainly, practitioners should take account of high-quality RCT-evidence and rely less upon low-quality evidence. But this is consistent with the additional claims that RCTs too can be very low quality, and that evidence from non-randomized studies can be very reliable, and that practitioners should avoid basing clinical decisions on poor-quality RCTs and should use high-quality non-epidemiological evidence. In other words, to adequately delineate Evidence-Based Medicine from its counterparts, stronger statements must be made, which rule out such alternative ideas.
One way to reformulate this would be: ‘RCTs can provide high-quality, reliable evidence, but non-epidemiological evidence cannot.’ Practitioners should base their decisions on high-quality RCTs where available, and limit their reliance upon non-epidemiological evidence, because it cannot be high quality. However, numerous EBM proponents clearly reject this strong version. Early EBM texts especially envisioned a role for non-epidemiological evidence, and several recent accounts acknowledge that non-RCT evidence can be high quality. The worry is that high-quality, reliable non-epidemiological evidence is relatively rare. In particular, Howick and his colleagues describe the conditions under which mechanistic reasoning (another pseudo-synonym in the ‘biological rationale’/ ‘pathophysiology’/‘physiologic rationale’ set) provides high-quality evidence about treatment effect-profiles. The conviction that only epidemiology provides high-quality evidence is not a necessary to be an EBM proponent.
Another reformulation strengthens the claim about RCTs and randomization, e.g.: ‘Randomization ensures that an RCT provides high-quality evidence.’ Coupled with the recognition that non-epidemiological and non-randomized epidemiological studies do not always provide high-quality evidence, the message to the clinician is to base their practice on reliably high-quality evidence (RCTs), rather than studies whose quality cannot be guaranteed. Although again some accounts have made such claims about the epistemic benefits of randomization,  numerous EBM proponents would baulk at such a suggestion. Many are aware that randomization is not a panacea of evidence-quality. The GRADE Working Group, an influential part of contemporary EBM, clearly argue that some RCTs provide moderate or low-quality evidence. Their ranking allows for RCTs to be down-graded from high-quality to lower quality levels for many reasons.
We have seen that the four main types of definition offered by EBM proponents are controversial even amongst EBM adherents. Some EBM proponents see Evidence-Based Medicine as a set of beliefs which they hold (but which others who also see themselves as EBM proponents may not), while others see EBM as something they do. Moreover, there is no real consensus about the underlying ideas which underpin these divergent definitions. To formulate a set of core ideas to which all EBM proponents can agree, the precepts must be weakened so much that they fail the test of specificity: they do not exclude alternative views or practices which are not classed as ‘EBM’. As such, they fail to constitute a definition of EBM. Surprisingly little common ground is shared across EBM proponents. I will argue for an alternative conceptualization of ‘EBM’ as a social movement within medicine, characterized as an association of individuals holding similar but distinct ideas, practices and goals, whose connection to one another is their self-identification with the movement.
The EBM Movement—‘Divided we Stand’?
Evidence-Based Medicine is not well-characterised as a particular way of practicing medicine or as a single set of ideas, principles or a distinct paradigm. Rather, EBM is best viewed as a social movement within medicine and biomedical science. I will first explicate the concept of a ‘movement’, and then show that EBM fits this description, before bringing out some of the consequences of this account.
Let’s first define a social movement as an association consisting of many individuals who share related ideas and practices, and are bound together by a common identification with the ‘movement’. Contrasting associations such as groups, factions or parties are more clearly united by a single principle or set of principles, and/or a single practice or set of practices. While parties and factions work together towards common aims and goals, movements have a looser association; they may have similar aims and goals, but do not necessarily share all aims. Members of a movement may also take very different paths towards their similar aims. 
A secondary characteristic of movements is a tendency towards informal power-structures, or absence of such structures entirely. Social movements are often described as “non-institutional”. There is no formal membership of the movement. Rather, ‘members’ are a part of the movement by their self-identification with it. By contrast, parties and factions tend to have clearly defined membership, leadership and internal social hierarchies. Membership and leadership structures are vital to ensuring that a single set of goals and principles is believed and promoted. A lack of centralised control facilitates members of movements to pursue their ideas and goals with a measure of independence. 
Another secondary characteristic of movements is the importance of charismatic figures to the successful spread of the movement. Because movements lack definitive central ideas or practices which are shared by all members, the spread of a movement (and the retention of existing members) relies upon members’ self-identification with the movement. An individual with similar ideas and practices to a social movement is not a member of that movement unless she identifies herself as such. The social movements literature distinguishes between adherents and constituents. An adherent shares similar ideas and practices to those within the movement. A constituent is a member (i.e. identifies herself as a member) of the movement. Adherence is necessary but insufficient for constituency. One may be an adherent but not a constituent if, for instance, one agrees with the ideas of a movement but not their goals or means of action.  Hence, for movements, making adherents become and remain constituents is key to successful growth.
Prominent examples of social movements include the labour movement, the civil rights movement, and communism. The labour movement (at least in recent European history) consists of a range of smaller groups who share similar but non-identical beliefs about working conditions and societal structures. The particular beliefs of these subsets and individuals vary. Some may advocate workers rights, others may not; some attempt to use political means, others deliberately avoid them; some favour industrial action, others reject it, etc. Although some groups within this movement have a defined leadership structure, the overall movement (at least traditionally) has no clear authority or direction. Each subset or individual is relatively free to pursue their goals and ideas. Anyone who does not self-identify with the labour movement is not part of that movement, even if they adhere to similar ideas.
Sociologists distinguish a number of types of social movement. Social movements attempt to cause and promote certain social changes. The extent and scope of these changes can be used to categorise movements. Two prominent dimensions are the scope of the change—whether the change is radical or relatively limited (“reformative”)—and the extent or target of the change—i.e. whether everyone is to be affected, or only those within the movement.  Aberle presents a classic four-part classification of social movements along these two dimensions. ‘Alternative movements’ seek reformative changes for the members of the movement. Many religious movements and ‘subcultures’ fall into this category. Where more radical, fundamental changes are sought for the movement’s members, the movement is classed as ‘redemptive’. Such movements include cults and societies such as the Amish. Other movements seek to change the whole society; these are classed as ‘reformative’ or ‘revolutionary’, depending upon the scope of the social change promoted. Reformative movements include many environmentalist movements, the prohibition movement in the USA, and trade unionism. Revolutionary movements include much of the communist movement and the civil rights movement.
Mainstream religions, subcultures, etc.
Cults, separatist societies, e.g. Amish.
Single-issue groups, e.g. environmentalism, prohibition—EBM.
Societal overhaul, e.g. Communism, civil rights, apartheid.
Representation of Aberle’s four-part classification of movements.
Evidence-Based Medicine is a reformative social movement within medicine. EBM adherents advocate change in the norms of medical practice, without a fundamental overhaul of the values of medicine. This change is novel, and is intended to affect the practice of both the members of the movement and the wider medical community. To defend this claim, I first show that Evidence-Based Medicine is a movement in the sense of possessing the primary and secondary characteristics described above.
The primary characteristic of a movement is the absence of a single binding idea or set of ideas, goals and practices which unite the group. Rather, the individuals advocate similar ideas, goals and practices, and the association is bound together by self-identification with that movement. The considerable differences in the characterisations of EBM discussed above make a prima facie case for this characteristic of EBM. Even those who advocate similar conceptions of EBM—for instance, the five linked ideas vs. Guyatt et al.’s ‘Principles’ approaches—are conspicuously different.
We might be concerned that such differences actually indicate a single, unified EBM ideology which has changed and evolved over time. Perhaps EBM began as a paradigm, became a process accompanied by the ‘five linked ideas’, and then evolved again to become advocacy of the hierarchy of evidence a la Guyatt et al. However, this interpretation is implausible. As we have seen, each of Four Ps are still defended in varying forms. Guyatt defended paradigm interpretations as recently as 2005, long after the two principles from the Users’ Guides were spelled out. Others continue to develop the classic process interpretation, and still others offer various forms of principles definition. The instances discussed above, though they have a distinct chronology, are merely prominent examples of such definitions as they came into vogue.
The concerns, goals and practices of individuals involved with the EBM movement vary. Many are primarily concerned with the improvement of clinical practice, but the ideas of how or why this is to be done range from the better provision and systematisation of evidence, to new philosophical approaches to evidence. Others see EBM as having a more limited role, similar to that adopted by the Cochrane Collaboration: providing critical summaries of the existing literature to clinicians and patients to counteract the challenge of the enormity of the medical literature. Some see EBM’s role as teaching clinicians to appraise evidence, while others advocate an intermediate layer of professional evidence-appraisers between the researcher and the practitioner.
This interpretation of Evidence-Based Medicine as a movement is corroborated by the presence of secondary characteristics of a movement. EBM has no clear leadership or power-structures. EBM grew from the McMaster Medical School, under the guidance of figures such as Gordon Guyatt and David Sackett. However, they exert no especial authority over EBM or its ideas. Influence tends to be mutual, and no individuals exert control over the EBM message.
Finally, Evidence-Based Medicine has spread through charismatic advocacy. Jeanne Daly’s detailed socio-historical study of influential figures within the movement repeatedly notes the charisma and determined proselytising behaviour of many EBM proponents. Sackett, Guyatt and Haynes are often described as charismatic figures , and Sackett especially was well-known for his international lecture tours, spreading EBM as widely as possible. EBM began as a new way of teaching medical students, and inspirational teaching remains a central plank of EBM advocacy. There is much talk of “conversion” to Evidence-Based Medicine, and critical parallels have been made to proselytizing, evangelism and religious advocacy. Even the name ‘Evidence-Based Medicine’ displays rhetorical acumen—the phrase makes disagreement with the movement seem like disagreement with basing medicine on evidence, in turn making practitioners reluctant to express dissent publically.
If Evidence-Based Medicine is indeed a reformative movement within medicine, what does this mean for our understanding of EBM and its impacts? By foregrounding the sociology of a movement, we learn several important lessons about EBM. First, we should not expect a single ideological definition of ‘Evidence-Based Medicine’ which would be acceptable to all, or indeed many, EBM proponents. There will be no set of principles which are both acceptable to most EBM proponents and sufficiently descriptive to distinguish EBM from its predecessors and rivals. In addition to finding that no single definition or definitional strategy captures ‘Evidence-Based Medicine’, we should expect that a range of aims and goals will be held by EBM proponents. Proponents will adopt many different strategies to effect different but related social changes.
Critics who target particular definitions should expect to be largely overlooked by many within the EBM movement, who will not see that definition as important to their ideology or group membership. The same can be said for criticising particular ideas defended by individual proponents. This leaves a difficult problem: how can those who want to evaluate the EBM movement proceed, if engaging with particular statements is unlikely to help? One response is to engage not with ideas, but with the effects and products of the movement. Once EBM is seen as a movement, a single line of enquiry becomes particularly salient: ‘Is the movement good for medicine?’ Perhaps the biggest effect of the EBM movement, their main product, is the pre-eminence hierarchies of evidence. Under the aegis of EBM, hierarchies have transitioned from a niche idea, used indicatively within clinical epidemiology, to a central pillar of the appraisal of all evidence in medicine. Hierarchies are used in clinical practice and public health, and by clinicians, healthcare providers and governmental bodies worldwide. Whether the EBM movement has been and is a force for good in medicine, then, is in large part bound up with the worth of hierarchies of evidence. If movements must be judged by their effects, and a major effect of the EBM movement is the proliferation of hierarchies of evidence, then appraising the value of hierarchies is a vital task in appraising the EBM movement.
 To provide an exhaustive account of the replications and quotations of the platitude would be an herculean task. Prominent examples include the Cochrane Collaboration’s ‘About Us’ page, numerous EBM proponents and critics alike. The entire platitude, in quotation marks, returns over 10,000 hits on Google.
 It is worth noting for the upcoming discussion that both Guyatt and Sackett’s platitudes conceptualise EBM as something done, not something believed—Sackett’s platitude equates EBM with the use of evidence, while Guyatt’s with the application of scientific method.
 Daly herself uses a more informative definition—she says: EBM is “the practical application of clinical epidemiology in patient care”. This definition, though not platitudinous, is at best partial—it omits the commonplace disparagement of non-epidemiological evidence and the importance of critical appraisal of both epidemiological and non-epidemiological evidence.
 Bhandari defends a paradigm definition. Another possible exception is Gordon Guyatt, who continued the paradigm terminology in an interview with Jeanne Daly. However, Guyatt’s attempt to define this ‘paradigm’ within the interview takes a typical ‘Principles’ approach, giving four key principles: (1) “clinical experience has severe limitations”, (2) “one needs rules of evidence that are, essentially, clinical epidemiology”, (3) “reasoning on the basis of physiology often proves misleading without empirical testing”, and (4) “a much lower value on authority”. Guyatt argues that taking this rational, scientific approach to the accumulation of one’s clinical experience brings one “into the new paradigm”.
 This approach originated in Users’ Guides XXV.
 Other EBM Processes have been presented, including six-step extensions of the process.
 “‘If the study wasn’t randomized, we’d suggest that you stop reading it and go on to the next article in your search’”; “determine if the study is randomized; if it isn’t, we can bin it.”
 In particular, Brian Haynes has focussed upon such search strategies to find ‘high-quality’ evidence.
 Such claims are fairly common in the epidemiological literature—the mistake is not exclusive to EBM, nor did it originate in the EBM literature.
 Another way to think about movements, to borrow a distinction from philosophy of science, is as unified but not united . Unification is the existence of links between members—a movement is unified by the individuals which compose it sharing (similar) ideas, goals and practices with certain other members, creating a network of links and relationships. By contrast, unity refers to the existence of a single ideology, goal(s) or practice(s) common to all within the group. Party unity is usually crucial to a party’s success. By contrast, unity is not required to keep a movement together, so long as the movement is unified by a network of similar ideas.
 Power structures in parties and factions are not necessarily hierarchical—collectives and committees may have a democratic power-structure, in which all members are equally represented; however, democratic power-structures still mandate all members’ adherence to the majority decision, unlike in the case of movements.
 One might also be an adherent but non-constituent for non-ideological reasons—for instance, disliking members of the movement personally.
 Some sociological theories (the “political process” theory of social movements) hold that the target of social movements is necessarily governmental. This would preclude Evidence-Based Medicine from classification as a movement, as the target is primarily clinicians rather than political institutions. However, recent studies of movements recognise a much broader range of targets.
 For instance, Sir Iain Chalmers on David Sackett: “David set off explosions all over the place … He converted many young people. He was only here for five years, but his mark on Europe as a whole is indelible. He is a very charismatic teacher.”