Towards a general theory of implementation
© May; licensee BioMed Central Ltd. 2013
Received: 13 August 2012
Accepted: 31 January 2013
Published: 13 February 2013
Skip to main content
© May; licensee BioMed Central Ltd. 2013
Received: 13 August 2012
Accepted: 31 January 2013
Published: 13 February 2013
Understanding and evaluating the implementation of complex interventions in practice is an important problem for healthcare managers and policy makers, and for patients and others who must operationalize them beyond formal clinical settings. It has been argued that this work should be founded on theory that provides a foundation for understanding, designing, predicting, and evaluating dynamic implementation processes. This paper sets out core constituents of a general theory of implementation, building on Normalization Process Theory and linking it to key constructs from recent work in sociology and psychology. These are informed by ideas about agency and its expression within social systems and fields, social and cognitive mechanisms, and collective action. This approach unites a number of contending perspectives in a way that makes possible a more comprehensive explanation of the implementation and embedding of new ways of thinking, enacting and organizing practice.
That we are never alone in carrying out a course of action requires but a few examples. Bruno Latour .
Understanding and evaluating the implementation of healthcare interventions in practice is an important problem for healthcare managers and policy-makers , and also increasingly for patients and others who must operationalize them beyond the boundaries of formal clinical settings [3, 4]. For the research community, applied research in this domain forms a focus for the new interdisciplinary field of ‘Implementation Science’ , and the development of implementation theory [6, 7] that provides a foundation for understanding, designing, predicting, and evaluating dynamic implementation processes. Implementation Science, like other closely related fields (for example, Health Services Research, Health Technology Assessment, and Improvement Science), needs comprehensive, robust, and rigorous theories that explain the social processes that lead from inception to practice.
This paper is intended to make a contribution to implementation theory. It does so by linking an existing theory – Normalization Process Theory [8–10], which characterizes implementation as a social process of collective action – with constructs from relevant sociological theories of social systems and fields, and from relevant social cognitive theories in psychology. The general approach here is to integrate these to provide a more comprehensive explanation of the constituents of implementation processes. This takes the form of a theoretical framework that characterizes and explains implementation processes as interactions between ‘emergent expressions of agency’ (i.e., the things that people do to make something happen, and the ways that they work with different components of a complex intervention to do so); and as ‘dynamic elements of context’ (the social-structural and social-cognitive resources that people draw on to realize that agency). The objective of this integrative approach to theory is to set out some of the core elements of a general theory of implementation. The theory presented is one that emphasizes agentic contributions and capability, and the potential and capacity for resource mobilization.
When people seek to implement a new way of classifying a disease, a new surgical technique, or a new way of organizing the transport of patients between hospitals, they express their agency (i.e., their ability to make things happen through their own actions). This is expressed in interaction with other agents, other processes, and contexts. Agents seek to make these processes and contexts plastic: for to do one thing may involve changing many others. Implementation therefore needs to be understood from the outset as a process – that is, as a continuous and interactive accomplishment – rather than as a final outcome. Moreover, ‘implementation’ never refers to a single ‘thing’ that is to be implemented. Whenever some new way of thinking, acting, or organizing is introduced into a social system of any kind, it is formed as a complex bundle – or better, an ‘ensemble’ – of material and cognitive practices. Even what appear as very simple implementation processes involve many moving parts. Throughout what follows, the term ‘complex intervention’ is therefore used to define the object of any implementation process [11–13].
Considerations of space mean that it is not possible to offer in this paper a comprehensive review of existing theories. (For major accounts of the problem of agency, routine and habituation, see Emirbeyer and Mische , Archer  and Camic , respectively. See also important papers by Grol et al., , Tabak et al., , Glasgow et al.,  and Damschroder et al. [19, 20], which review the bases of analytic frameworks and their application.) Other, important theory-based frameworks for implementation have also been developed using integrative techniques. In management science, the highly influential Diffusion of Service Innovations model proposed by Greenhalgh et al. , adds constructs from social psychology, organizational behavior theories, and socio-technical systems theory to produce a typology of factors that affect diffusion into practice. The Technology Acceptance Model utilized by Venkatesh et al.  also added a group of ‘diffusion’ constructs to those proposed by the Theory of Planned Behavior . It appears to be predictive of intention to utilize behaviors, interventions and innovations . The Theoretical Domains Framework also builds on multiple theories, combining constructs from different sources . The Technology Acceptance Model and the Theoretical Domains Framework are both intra-disciplinary models that focus on individual differences and make an important contribution to understanding and evaluating change.
In the complex realm of emergent social and organizational processes of intervention and innovation, a general theory of implementation is likely to require more than an intra-disciplinary model. The range of phenomena involved means that an inter-disciplinary perspective that draws on insights from sociology and psychology is likely to offer a more comprehensive explanation of implementation processes.
The work presented in this paper is integrative. It takes a set of already existing theoretical constructs and links them together in a new way. The first part of this work (in the introduction and the first section of the discussion) sets out some key definitions of terms that underpin the agentic approach taken here. This approach is founded on the notion that implementation expresses ‘agency,’ and should be understood and evaluated against the problem of how human agents take action in conditions of complexity and constraint.
In the second part of the discussion, four key elements of a general theory are laid out. These are expressions of agency within implementation processes, characterized through constructs of capability and contribution; and dynamic elements of the context of implementation, characterized through the social structural and social cognitive resources upon which agents draw when they take action – these are encompassed by constructs of capacity and potential. Each construct is described, its genealogy registered, and its core components or dimensions are defined. Each construct is also reduced to a single context-independent proposition.
The aim of implementation theory is the development of a robust set of conceptual tools that enable researchers and practitioners to identify, describe and explain important elements of implementation processes and outcomes. The proposed general theory presented here links together a set of constructs drawn from other theories. When integrated, these begin to comprehensively describe and explain elements of the processes by which implementation, embedding and integration take place. These constructs are anchored to a central theoretical claim, which is that social and cognitive processes of all kinds involve social ‘mechanisms’ that are contextualized within social systems and from which spring expressions of agency. However, before moving on to the constructs of the theory, some key terms first need to be defined.
Before discussing the constructs of the theory, it is worth being clear about what is meant by some key terms. For the purposes of this paper, a social system is defined as a set of socially organized, dynamic and contingent relations. These relations form a structure that is populated by agents (who may be individuals or groups) that interact with each other. Information and other resources flow through these interactions between agents. As Scott notes, social processes cannot be understood without reference to social systems . A system therefore forms structural conditions for the expression of agency. Social systems are emergent, which means that they are shaped, over time and across space, by both endogenous and exogenous factors. This means that their future is relatively unpredictable.
Within emergent structural conditions, social mechanisms operate. In this paper, a mechanism is defined as a ‘process that brings about or prevents some change in a concrete system’ , that ‘unfold[s] over time’ , and expresses contributions of human agency . The value of a mechanism’s focused approach is that it helps us understand the means by which humans act on their circumstances and try to shape them. Here, ‘agents jointly construct their own actions as pragmatic, strategic responses to their circumstances and as expressions of commitment to their values’ . In this context, a mechanism-based approach focuses on the things that agents do to make their affairs plastic or malleable.
Taken together, emergence in social systems and plasticity in social mechanisms mean that the future shape and form of any social process is uncertain. This is a view shared, for good reasons, by proponents of very different theoretical positions – from systems theory , to the sociology of science and technology . Ideas about the importance of social mechanisms as explanations of social processes have become important as the social sciences have sought to deal with problems of contingency and causation [29, 32, 33].
Finally, we need a definition of implementation. For the purposes of this paper, implementation can be characterized as a deliberately initiated process, in which agents intend to bring into operation new or modified practices that are institutionally sanctioned, and are performed by themselves and other agents . These act to modify a social system. As this happens, agents – who are the individuals and groups that encounter each other in healthcare settings – engage in the realization and mobilization of material and cultural resources, and secure the consent, cooperation and expertise of those other agents who inhabit the particular field or domain of action in which the process of implementation takes place [8, 34–36]. Implementation subsumes all related activities from initiation to incorporation , and it may lead to the routine incorporation of ensembles of practice in everyday work [38, 39].
A theory stands or falls on the extent to which it actually illuminates and explains a set of phenomena. To perform this function it must offer a general, and context-independent, cognitive model that simplifies those phenomena. In this section of the paper, the four constructs – capability, capacity, potential and contribution – that are brought together to form the general theory are described. The relationship between these constructs is shown in Figure 2. Each of the construct descriptions outlines its theoretical antecedents, characterizes its core components or dimensions, and reduces the construct to a single context-independent proposition. The structure of concepts, constructs and dimensions is shown in Figure 3.
This section sets out the elements of the theory in the most general way, but it does not show how the theory can be operationalized in a context-dependent setting. So, in the section that follows, a worked example of the theory-in-use is presented. This applies the constructs directly to a practical problem – the implementation of nursing clinical practice guidelines – and shows how each of the theory’s general propositions can be translated into a context-dependent proposition that looks much more like a research hypothesis.
The first construct to be discussed is that of capability. The question of what is being implemented is always more complex than might be supposed. For the purposes of this paper, the object of an implementation process is subsumed under the ambit of a ‘complex intervention’  – a cognitive and behavioral ensemble that involves different material and cognitive practices, relations and interactions. When agents engage with complex interventions, they engage with multiple objects of practice. These may include classifications, real or virtual artifacts and techniques, technologies or organizational systems. A complex intervention may include all of these, and this is an area of significant interest in the social sciences. It includes landmark studies by Burri on MRI scanners , and by Yoxen on the development of ultrasound . New or modified ensembles of practice are often intended to change people’s expertise and actions, illustrated well in Smith et al.’s, study of anesthesia handovers . Much work in this field has critically interrogated the development of informatics applications. See, for example, Berg’s study of decision-making tools , and Nicolini’s  and Lehoux’s  work on telemedicine systems. These studies have shown how the attributes of the components of complex interventions themselves affect their use. Such attributes include their virtual or physical character , the assumptions about use and users that are embedded within them [47, 48], their complexities in practice and in the social relations that they engender , and their expected value. All of these elements combine to make them much more than the sum of their parts and to shape the relations between agents and the different components of a complex intervention through processes of mutual co-constitution [50–52].
The qualities of complex interventions – whether they are workable in, and can be integrated into, practice – are therefore important elements of implementation processes. In an earlier paper , it was shown that workability can be divided into the actual material practices that agents perform when they operationalize a complex intervention (its interactional workability), and the ways in which these practices were linked to, and distributed through, a division of labor (its skill set workability). Equally, integration can be divided into contextual integration, in which the performance of a practice is linked to the means by which it is realized and to the resources transmitted to it, and relational integration, in which the performance of a practice is linked to the means by which users make themselves and others accountable for its performance. Some existing frameworks have utilized workability constructs from diffusion of innovations theory [20, 24, 53], setting out, for example, ideas about ‘trialability’ and ‘ease of use’ as being important components of such models. The risk here is that these come to be seen as qualities of the objects themselves, rather than expressions of the capability of their users that are, in turn, derived from the interactions between them. Users make objects workable through use, and they work to integrate them in their social contexts.
Workability: the social practices that agents perform when they operationalize a complex intervention within a social system, and characterizes interactions between users and components of a complex intervention;
Integration: the linkages that agents make between the social practices of a complex intervention and elements of the social system in which it is located, and characterizes interactions between the context of use and components of a complex intervention.
P1. The capability of agents to operationalize a complex intervention depends on its workability and integration within a social system.
The implication of this is that a complex intervention is disposed to normalization into practice if its elements, and their associated cognitive and behavioral ensembles can be made workable and integrated in everyday practice by agents. If workability and integration cannot be sustained, then the embeddedness of the complex intervention will be threatened as the capacity of agents to employ it is confounded.
Much work about the diffusion of innovations has started with the notion that advances in technology or practice flow through, and gradually populate, large scale social networks [54, 55]. They can do this because they possess attributes that make them attractive to different kinds of ‘adopters’ . Greenhalgh et al.’s  important review of diffusion of service innovations studies introduces 53 measurable attributes to this model . The existence of particular kinds of social networks are important antecedent conditions for implementation processes, because they provide relational contexts for the reciprocal chains of interactions and flows of information that form social systems . The mechanisms involved in flows of ideas and innovations spread are often unclear, but are assumed to be like those of mimesis or contagion . However they work, networks form relational pathways through which different kinds of work are done. This means that they are accomplishments rather than static structures, and that these accomplishments include information flows and practices of operationalization of the complex intervention.
Social networks may overlay relatively ‘open systems’ that are diffuse and unbounded, and they often transcend formal institutional boundaries . An example might be a population dispersed over many organizations of different sizes, and distributed in social space, like the physicians studied by Coleman et al., in their classic study of the diffusion of pharmaceutical products . Or, they may overlay relatively ‘closed systems’ that appear to be highly structured and bounded. These may be specific organizations, or work groups, like those discussed by Whitten in her work on the diffusion of telemedicine services [61, 62]. They may also take the form of highly structured and bounded networks that exist within – or between – organizations. An interesting example is that of the networks involved in designing, delivering and participating in large randomized controlled clinical trials . These can be complex and widely distributed (often internationally) but remain highly structured and have robust mechanisms to ensure their closure.
The ability to engage others in collective action is a social skill that proves pivotal to the construction and reproduction of local social orders (…) Social life revolves around getting collective action, and this requires that participants in that action be induced to cooperate. Sometimes coercion and sanctions are used to constrain others. But often, skilled strategic actors provide identities and cultural frames to motivate others .
This kind of theoretical perspective enables the analysis of basic conditions for the expression of agency that participants invest in implementation. They exercise their capacity to do this in fields that may be hierarchically nested and, or, overlapping and that provide interactional structures for the variable distribution of people, power and resources. Within these bounds, participants are characterized by a variety of context-dependent affiliations, social roles, and rules in the form of social norms and conventions. These may include the capability to define and regulate conduct by consensual or coercive means .
Social norms: institutionally sanctioned rules that give structure to meanings and relations within a social system, and that govern agents’ membership, behavior and rewards within it. They frame rules of membership and participation in a complex intervention.
Social roles: socially patterned identities that are assumed by agents within a social system, and that frame interactions and modes of behavior. They define expectations of participants in a complex intervention.
Material resources: symbolic and actual currencies, artifacts, physical systems, environments that reside within in a social system, and that are institutionally sanctioned, distributed and allocated to agents. They frame participants’ access to those material resources needed to operationalize the complex intervention.
Cognitive resources: personal and interpersonal sensations and knowledge, information and evidence, real and virtual objects that reside in a social system, and that are institutionally sanctioned, distributed and allocated to agents. They frame participants’ access to knowledge and information needed to operationalize the complex intervention.
P2 . The incorporation of a complex intervention within a social system depends on agents’ capacity to cooperate and coordinate their actions.
The implication of this is that a complex intervention is disposed to normalization into practice if the social system in which it is located is one that provides normative and relational capacity – through which agents resource, cooperate, and coordinate their investments and contributions to its use. If capability cannot be sustained, then the embeddedness of the complex intervention will be threatened as its context of action decomposes.
a temporally embedded process of social engagement, informed by the past (in its habitual aspect), but also oriented toward the future (as a capacity to imagine alternative possibilities) and toward the present (as a capacity to contextualize past habits and future projects within the contingencies of the moment) .
treats organizational readiness as a shared team property – that is, a shared psychological state in which organizational members feel committed to implementing an organizational change and confident in their collective abilities to do so. (…) Some of the most promising organizational changes in healthcare delivery require collective, coordinated behavior change by many organizational members .
Individual intentions: agents’ readiness to translate individual beliefs and attitudes into behaviors that are congruent, or not congruent, with system norms and roles. They frame individual motivation to participate in a complex intervention.
Shared commitments: agents’ readiness to translate shared beliefs and attitudes into behaviors that are congruent, or not congruent, with system norms and roles. They frame shared commitment of participation in a complex intervention.
P3. The translation of capacity into collective action depends on agents’ potential to enact the complex intervention.
The implication of this is that a complex intervention is disposed to normalization into practice if agents both individually intend and collectively share a commitment to operationalizing it in practice. If potential cannot be sustained, then the embeddedness of the complex intervention will be threatened as agents’ commitments are withdrawn.
To be an agent is to intentionally make things happen by one’s actions. Agency embodies the endowments, belief systems, self-regulatory capabilities and distributed structures and functions through which personal influence is exercised, rather than residing as a discrete entity in a particular place. The core features of agency enable people to play a part in their self-development, adaptation, and self-renewal with changing times .
[F]orms of joint action can unite two or more individuals towards a shared end. In joint action, disparate individuals are coordinated in such a way that they become centered on each other (…) and are able to act collectively, as if they were a single entity. In certain circumstances, then, complex structures of jointly acting individual agents are able to act as collectivities .
Coherence or Sense-Making: agents attribute meaning to a complex intervention and make sense of its possibilities within their field of agency. They frame how participants make sense of, and specify, their involvement in a complex intervention.
Cognitive Participation: agents legitimize and enroll themselves and others into a complex intervention. They frame how participants become members of a specific community of practice.
Collective Action: agents mobilize skills and resources and enact a complex intervention. They frame how participants realize and perform the intervention in practice.
Reflexive Monitoring: agents assemble and appraise information about the effects of a complex intervention within their field of agency, and utilize that knowledge to reconfigure social relations and action. They frame how participants collect and utilize information about the effects of the intervention.
P4. The implementation of a complex intervention depends on agents’ continuous contributions that carry forward in time and space.
The implication of this is that a complex intervention is disposed to normalization into practice if agents invest in operationalizing it in practice. If contribution cannot be sustained, then the embeddedness of the complex intervention will be threatened as agents’ efforts diminish.
In the preceding section, the general theory was presented as a set of context-independent constructs, dimensions and propositions. The question that arises from this is, how would we use this general theory to structure understanding of an implementation process? This is as much a methodological question as it is a theoretical one, but it is important to illustrate the theory in action. In this section of the paper, the context-independent constructs and propositions of the theory are translated into the context-dependent form of a worked example.
The worked example will be presented in two stages. First, a theory-informed narrative of the implementation of a new clinical practice guideline for nurses will be presented. Second, the context-independent propositions of the general theory will be translated into context-dependent ones, to provide a specific theoretical framework for planning and evaluating the implementation of clinical practice guidelines.
It must be emphasized that this is a worked example of a theory in practice, not a formal data analysis or review, but it does draw on information from seven studies [81–87] that have met the quality criteria for inclusion in a systematic review of qualitative studies of nursing guideline implementation informed by Normalization Process Theory.
The starting point for the worked example is to consider the dynamic features of context in which an implementation process takes place. Here, the implementation of a clinical practice guideline is an intentional modification of the existing routinely embedded relationships and practices through which the hospital department is constituted a social system. These are already highly structured, with formal and informal norms that govern the conduct of work by nurses and other professionals, and well-defined professional roles that they assume when they do so. At the same time, nurses working in this setting have available to them a body of cognitive and material resources that provide the basis of knowledge and practice for their work. These social-structural resources make being a nurse and doing nursing work possible. The introduction of the guideline changes to some extent their organization and allocation. By definition, it changes the rules or norms that govern the conduct of work and, if it involves the re-allocation of work from one group of professionals to another, it may also change their roles. Introducing the guideline may also change the distribution and availability of material and cognitive resources available to nurses and other professionals.
In circumstances where nurses did not cooperate with each other over changing norms or roles, or resisted the coordination of changes in material and cognitive resources, we might expect the prospects for normalization of the guideline to diminish. There is of course a second dynamic feature of context, which is the potential of nurses to engage with the work of operationalizing the changes that implementing the guideline brings with it. In this context, the attitudes and intentions of individual nurses (especially in situations where they have a high level of personal autonomy) are important. These play into a wider set of shared commitments, in which nurses build a sense of collective readiness, not simply to enact the guideline but also to work to accommodate the other changes that it will bring. In this context, collective readiness is interdependent with, but not simply the sum of, individual attitudes. As Weiner points out , shared commitments is a complex phenomenon, but plainly this is also highly relevant to the problem of capacity. The relationship between potential and capacity is a complex one, since nurses’ understandings of what must change during the implementation of a guideline are likely to shape readiness to act. Certainly within social systems of all kinds, dynamic elements of contexts such as those specified by notions of capacity and potential shape each other. But they also continuously interact with emergent expressions of agency as a social process is formed.
Turning now to emergent expressions of agency, we can begin by thinking about how nurses work upon a clinical guideline. A clinical practice guideline is a set of procedures that are intended to govern practice, and which are embedded in software (perhaps in an electronic healthcare record, or some other system) or in hardware (in a bedside card, paper record, or printed set of standard operating procedures). It will embody a set of assumptions about the context in which it is to be used, and about the nature of the user, which will in turn shape its relationship with that context and structure the way that it is practically used. So, rather than seeing the guideline as a ‘thing’ to be implemented, it is better understood as a set of practices. These have varying degrees of workability (the ways in which they can be deployed and acted upon by their users) and integration (the ways in which they express expectations of their users and conditions of use). These assumptions and expectations may not be correct – indeed, a common experience of implementation of complex interventions of all kinds is that they need to be locally reinterpreted and modified in practice – and the use of a guideline may have unanticipated consequences, even if it is deployed as intended.
Finally, while nurses are able to draw upon and mobilize social-structural and social-cognitive resources and potential as they proceed through the implementation of a clinical guideline, and while their capability to do so is related to its workability and integration, it is the actual doing of the guideline in practice that matters. This is important because there are ample examples of the implementation of complex interventions where individual and shared commitment to implementation is revealed to be low, and where the social and cognitive resources available to nurses are massively disrupted, and yet professionals are able to reconfigure practice to make it ‘work’ – and vice versa. So it is what nurses actually do when they implement a clinical practice guideline that must be at the center of analysis.
The basic claim of the theory  is that the course of an implementation process is governed by the operation of social mechanisms that are energized and operationalized through agents’ contributions. In this case, it means that nurses work to make sense of the guideline and work out how to put it into action. In this context, they need to think through what the guideline will mean for practice (and how it will make practice different). This sense-making work may be quite informal, but it fulfills an important function, which is to make the body of everyday work into a coherent whole and to give it a sense of orderliness. At the same time, all of the participants in the implementation of the guideline – who may also include patients, their significant others, and other professionals and administrators – also need to find ways to bring about a community or practice in which the guideline is seen as initiating and enrolling them into a legitimate reconfiguration of practice. These are important antecedents for ‘doing’ the guideline in practice because they form points of connection between nursing work and its structural and cognitive resources, but they are also continuing accomplishments as the guideline is enacted in everyday practice.
It is collective action – nurses working together to put the guideline into practice and continually using it with their patients (or not) that is the central element of the implementation process. For it is here that the guideline ultimately becomes normalized and disappears from view as it becomes the ‘way we do things here.’ As this collective action continues, so too does the work of appraisal – which may be some formal evaluation of the guideline, but is almost certainly also an informal collection of experiential accounts and implicit theories about why things turn out as they do. The theory depends on this notion of agentic contributions (and the investments in agency through which they are formed). It is that agents (who may be individuals and groups) mobilize resources (which may be both structural and cognitive) and then invest them in enacting the ensemble of practices that make up the work of implementation.
Focusing on the implementation of clinical practice guidelines in nursing is interesting. They are hard to implement. Implementation and embedding in practice take place in complex organizational and clinical environments, in circumstances where time is both a scarce personal asset and an expensive corporate asset, and where work of one kind is constantly squeezed by other demands. This forms the background of a theoretical narrative that accounts for implementation – in the wider contexts of multiple sources of contingency and a wide variety of confounding factors – the next step is to take that theoretical narrative and translate the theory’s propositions into a context-dependent form. Taking this step is important because the purpose of the theory is to help facilitate both prospective understanding of implementation processes and evaluation of their outcomes.
Capacity: The implementation of a clinical guideline in its practice setting depends on nurses’ capacity to: (i) cooperate to operationalize changing norms and roles; and (ii) coordinate their operationalization of changing material and cognitive resources.
Potential: The translation of nurses’ capacity into contributions to practice change depends on the degree of: (i) their individual intentions; and (ii) their shared commitments to enact the guideline.
Capability: The capability of nurses to implement and embed a clinical guideline in everyday practice depends on its qualities of: (i) workability at the bedside; and (ii) integration within nurses’ workflow.
Contribution: The implementation of a clinical practice guideline depends on nurses’ continuous contributions of agency to: (i) continuously enact it; and (ii) carry it forward as an element of future work.
Once again, the contingent relations between these two constructs (and their relations with dynamic elements of their context) must be determined empirically. For each of these, we now have a pair of context-dependent propositions. These can be worked up as specific hypotheses for a prospective study of guideline implementation, but at the moment they function as a low-level theory. Once again, this is important: translational theories such as this one provide a realistic degree of granularity, both for planning an implementation process, and evaluating its progress and outcomes.
Thus far, the possible constructs of a general theory have been outlined; key components of these constructs have been identified and defined; and a set of propositions have been laid out. The first of these characterize domains in which social mechanisms operate, the second characterize specific foci of empirical investigation and measurement, and the third provide the foundations for a set of testable hypotheses about the course and direction of implementation processes themselves. These can be combined with those set out in two earlier papers [8, 29] to provide a more comprehensive explanatory model of processes of implementation, embedding and integration of complex interventions.
The description of constructs, thus far, shows a set of mechanisms that energize and shape implementation processes. It also suggests how endogenous factors might confound these processes, for example through the withdrawal of agents’ shared commitment to a complex intervention, or through some failure of workability and integration. Plainly, there are many reasons why implementation processes take the form that they do. Many of them involve exogenous factors. Fligstein and McAdam  call these ‘shocks,’ and they also include what proponents of actor-network theory call ‘contingencies’ , which arise outside of the fields in which the implementation process takes place. Their effect is best determined empirically: there is no need to account for every possible permutation of contingency and confounding. We know for example that wars; epidemics; financial crises; changes of government, law and policy; organizational strategizing, collapse or takeover; resistance and recalcitrance on the part of other systems of practice; and the emergence of other new techniques and technologies all have such effects. However, in such circumstances, agents often continue to invest in overcoming turbulence and recalcitrance, and seek to make their effects malleable and plastic.
Limits must be placed on integrative theories such as this one. First, psychological and sociological theories that have been drawn on here variously place individual cognition and agency at their centers, while others give primacy to social processes. For the moment, we have to put this problem to one side; the debate about the relationship between structure and agency is a meta-theoretical problem. At a more practical level, although a comprehensive theoretical model of implementation processes would be a valuable tool for practitioners and researchers, the phenomena that are involved are so numerous, variable and complex that it may be that they cannot be fully captured. In relation to this, it is important to note that comprehensiveness and omniscience are not the same thing, just as federation and unification are also different. The aim in this paper is to move towards a general theory by producing a more comprehensive model, not by enumerating all phenomena and unifying all possible theories.
Finally, while sensitivity to theory and awareness of its diverse forms and purposes is a normal part of the training of social scientists, the integration of constructs belonging to different theories is an under-explored problem of method . There is no universally accepted technique for accomplishing this task. These limits aside, the strength of the analysis offered here lies in its middle-range operationalization and the modest claims that are consequent to this.
At a time when most healthcare systems are under tremendous pressure, why should we be concerned with theory? Surely there are enough theories, and there are enterprises that are more practically useful to policy-makers, clinicians and researchers? The justification for doing such work is, in this context, a simple one. There is much evidence about the clinical and cost-effectiveness of new and existing treatment modalities, and ways of delivering and organizing care. What ‘works’ is – in many fields – established through rigorously designed and applied outcomes studies. But it is far less clear, to clinicians in practice as well as to policy-makers and managers, how to get these advances in healthcare and its delivery into practice, and – on that implementation journey – how to understand the factors that will promote or inhibit their passage. Robust theories form the foundation for rigorous research to inform implementation journeys .
The claim of a general theory is one that invites hubris, and the claim that this work is on a journey towards a general theory only reduces this prospect a little. However, implementation science is a field where interest in developing and testing new theories and theory-informed evaluation and planning frameworks is exploding. This makes the field intellectually exciting and practically interesting. It is against this background that the proposed General Theory has developed.
As Figure 1 suggests, the theory presented here is a waypoint on another kind of continuing journey, too. This is a theoretical journey that began with the development of a formal grounded theory (the Normalization Process Model [34, 38]) that explained aspects of the routine incorporation of complex healthcare interventions into practice. This model was then developed into Normalization Process Theory, a generic and middle-range theory of implementation [8, 10]. In the present paper, the theory has been further extended. Integrated with constructs from other theories, a more comprehensive set of explanations for implementation processes is formed. Integration has included constructs related to the structural properties of social systems, and individual and shared intention, to those related to the attributes of complex interventions and to the collective action of their users. The approach taken throughout has been to sketch out social processes and relationships and their associated mental and social mechanisms. In this context, including perspectives from higher level accounts of socio-technical change , agentic perspectives in social cognitive psychology , and social theories of structure and action  – permits more comprehensive explanation.
The four constructs derived from this work – capacity, potential, capability and contribution – define the core of a parsimonious and workable general theory of implementation based on social mechanisms. The relationships between them are mapped in Figure 3. They have regard for the dynamic elements of the contexts and objects of implementation, and for the dynamic potential and actual expressions of agency. These form the social processes through which implementation is accomplished. They are not linear or sequential, but interact continuously with each other in emergent and complex ways. Agents’ experiences of these processes vary across social time and space, as they are shaped, encouraged and confounded by other endogenous and exogenous factors. Importantly, these constructs and their relationships with each other are not resistant to formalization. The propositions that are associated with them open this up. They represent properties of implementation processes that are multidimensional and multifactorial, but which are amenable to empirical investigation and measurement . These properties are summarized in Figure 2, which sets out the hierarchy of constructs of the theory linking each level to the problem of organizing the complexity beneath.
An implementation process involves agents in the intentional modification of the social systems that occupy a field, or fields, of action.
Within social systems, emergent expressions of agency both shape, and are shaped by, dynamic elements of their contexts. They continuously interact to form an emergent social process.
Emergent expressions of agency and dynamic elements of context continuously interact with both endogenous and exogenous contingencies and confounders.
Agents work to negotiate the effects of interactions, contingencies, and confounders. They seek to make these plastic and shape them through their agentic contributions, and thus to govern the conduct of an implementation process and its outcomes.
Each of these characteristics of an implementation process also corresponds to a ‘level’ of analysis in the hierarchy of constructs shown in Figure 2.
In the work that has led to this paper, only constructs that characterize social or cognitive mechanisms associated with agency, and that are linked to empirical research, have been utilized. The constructs offered here are ones that can be traced back to rigorous studies that have robustly investigated processes, relations and mechanisms that have actually been shown to matter in studies of implementation and its related phenomena. The theory thus characterizes implementation processes from a position of strength. It provides a framework for thinking and planning the implementation of complex interventions, as well as a point of departure for measuring and evaluating progress and outcomes. Such interventions are to be found everywhere. They exist not just in healthcare but also in government, business, and military operations.
Work leading to this paper was partly funded by ESRC Grant ES-062-23-3274, and this support is gratefully acknowledged. I thank Chris May for very detailed comments on several drafts of the manuscript. My work with Mark Johnson and Andy Sibley led to invaluable contributions to the theory presented here. I also thank Chris Dowrick, Tracy Finch, Peter Griffiths, Frances Mair, Anne MacFarlane, Elizabeth Murray, Catherine Pope, Mary Ellen Purkis, Tim Rapley, and Anne Rogers for their comments and criticisms of the arguments presented here. I draw attention the prepublication history of this paper to show how an intellectually generous group of peer reviewers can shape a paper for the better.
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.