In the last decade or so, cognitive behavioural therapies have been developing in a variety of ways. Their evidence base has been burgeoning, they are becoming increasingly adopted by the clinical services, and they are diverging into a ‘family’ of related approaches with somewhat diverse influences, such as mindfulness, attachment theory and meta-cognition. Nevertheless, as I have mentioned elsewhere (Mansell, Reference Mansell2008), there remain a range of challenges concerning, for example, the degree to which CBT can be said to have a clear, coherent link between its theory and its practice, and issues over how it is provided in an accessible way to a wide range of client groups. The term CBT itself belies an uneasy alliance between cognitive theory and behavioural theory (a topic of one of the articles in this special issue), which use different terminology and make different assumptions about the importance of internal mental states and observable behaviour.

I came across Control Theory initially through the work of Carver & Scheier (Reference Carver and Scheier1982) which, among others, influenced the development of the cognitive model of social phobia (Clark & Wells, Reference Clark, Wells, Heimberg, Liebowitz, Hope and Schneier1995). However, it was only later that I accessed the original work on Control Theory that Carver and Scheier utilized – Bill Powers’ (Reference Powers1973, 2005) book Behavior: The Control of Perception, a fuller exposition of an earlier paper (Powers et al. Reference Powers, Clark and McFarland1960). This provided a full and detailed expansion of the theory which came to be known as Perceptual Control Theory (PCT). The theory provided a breath of fresh air to me in terms of what ‘theory’ really means within psychology, and it appeared to resolve the strain between cognitive and behavioural accounts in the literature. The theory is both familiar and radical; it makes the uncontroversial claim that behaviour is goal-directed; yet in specifying the exact mechanisms for this to occur, reveals an architecture of the mind that is unique and highly versatile. Having read thoroughly about PCT, I promptly completed a review paper on this topic, which was eventually published a few years ago (Mansell, Reference Mansell2005). Within a few months of this publication Tim Carey contacted me. He had been well acquainted with PCT for many years and had been delivering and training a form of therapy, Method of Levels (MOL) based on PCT in Fife, Scotland, for the previous 5 years. We met shortly after, I learned MOL and we began a process of clinical training, research and dissemination involving PCT and MOL. The special issue of The Cognitive Behaviour Therapist represents a consolidation of current work on Control Theory within CBT and hopefully provides a step towards the wider acceptance and use of Control Theory approaches.

Very aptly, the first article in the special issue is written by Bill Powers, who developed the foundations of control theory and human behaviour in the 1950s. It is both a recognition of both the longstanding challenge of acceptance of PCT in mainstream psychology, and Bill's own persistence through the pre-eminence of both behavioural and cognitive movements since the 1950s, that he is willing and able to contribute to this special issue in 2009. In his article, he explains the origins of his work within engineering and the parallel beginnings of Method of Levels (MOL), and thereby sets the stage for the later clinical practice articles. In the next review paper, Tim Carey and myself explain one of many implications of taking a control theory perspective – it makes clear the limitations of attempts by CBT researchers to try to ‘dismantle’ cognitive from behavioural processes of change. Our article explains the problematic assumptions within these research designs and also serves to introduce the concept of ‘control’ as the function of a connected working system from which ‘cognition’ and ‘behaviour’ cannot be separated.

Two papers report research studies to test the validity of a control theory approach to psychological distress. Stuart Reid reports a study of the relationship between intrusive imagery and personal goals in clinical and non-clinical groups which illustrates their close connection and explains this from a control theory perspective. Timothy Bird and colleagues report systematic analyses of a single therapy session which illustrates the process of therapy from a control theory perspective and the formulation of conflicting hierarchical goals that it reveals.

In the first of a number of practice articles, Tim Carey more fully explains MOL as a cognitively-orientated psychological intervention that, through a simple process, helps clients to manage and overcome a range of presenting problems. My article that follows introduces PCT and MOL and is explicit about its benefits and difficulties. In particular, it aims to help CBT therapists make their own decisions about its utility, and how and when to incorporate MOL within their own practice. Chris Spratt and colleagues provide clinically generated formulations of a series of cases utilising control theory that highlight the role of goal conflict in psychological distress. PCT also has intriguing implications for how therapies are delivered. Tim Carey and Margaret Spratt explain the positive implications of how taking a control theory perspective encourages a fully client-centred service in which the number and frequency of therapy sessions are largely determined by the user. Finally, Sara Tai concludes with an overview of how MOL can be used flexibly in the practice of CBT, even in the most challenging of clinical populations – people with psychosis. A particular strength of this article is its use of a versatile understanding of PCT to address a range of difficult situations that arise in clinical practice.

I hope that you will have the time to acquaint yourself with Control Theory through the papers in this special issue – PCT is both a theoretical perspective on how to adapt current CBT (see also Watkins, Reference Watkins2008; Brady & Raines, Reference Brady and Raines2009) and a window to new forms of clinical practice. Further extensive information on PCT is available at www.pctweb.org. Please read on, and in true Control Theory spirit: ‘feedback’ is welcome!