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Introduction

The quest for certainty blocks the search for meaning.

-Erich Fromm.

Cognitive behavioural therapy (CBT) has established itself as the dominant force in western psychotherapy. It has been identified as the treatment of choice by a range of health agencies, such as the UK National Institute of Clinical Excellence (NICE), for many of the most commonly encountered forms of psychological distress. In the United Kingdom and elsewhere, training in CBT has greatly expanded in an effort to increase public access to this form of evidence-based therapy. This has caused considerable alarm to proponents of non-CBT models, some of whom have taken a highly critical and challenging stance to what they perceive to be 'the CBT tsunami' (Dalal, 2018). Others have become so alarmed that they fear the advance of CBT will lead to the prospect of '100 years of psychotherapy wisdom' being lost (Lees, 2016). During the 1990s, there appeared to be the possibility of further developments towards more integrative ways of practising. Indeed, one view of CBT has always been that it was intended to be a form of integrative therapy (Alford & Beck, 1997). In the current situation of the rapid expansion of CBT, there appears to be a hardening of views, with critical discussions around CBT appearing to have a limited impact due to their tendency to adopt and then attack 'straw man' versions of CBT that the CBT practitioner is unable to recognise (see the collection of papers in House & Loewenthal, 2008, for a range of both straw man and reasoned critiques).

From the outside, it can appear as if CBT is sitting proudly, if unjustifiably, on its laurels and is immune to any form of challenge. At the same time, within CBT there remains a range of unresolved clinical, empirical, theoretical and philosophical dilemmas and controversies. It is widely accepted that, rather than being a unified school of therapy, CBT is in fact a diverse range of therapies and theories that display both a family resemblance and significant points of disagreement. In a controversial paper, Hayes (2004) argued that there exists three generations, or 'waves', of CBT. The first wave, originating in the 1950s, focused on the identification and application of basic principles of learning. The second wave, originating in the work of Beck and Ellis, as well as the social learning theory of Bandura, shifted the focus to cognitive mediation of behavioural and emotional change. Hayes (2004) argues that the second wave also involved the loss of a strong link between the applied techniques of CBT and basic laboratory-based science on fundamental principles; instead, the second wave favoured a more clinical approach to the evaluation of efficacy of treatment packages for specified diagnoses, formalised as treatment manuals. The third wave, according to Hayes (2004), came to fruition in the late 1990s and has involved an emphasis on assisting clients to change their relationship with cognitions and other distressing psychological experiences-instead of direct cognitive change efforts, mindful awareness and acceptance of distressing experience is promoted along with the identification of forms of value consistent behaviour.

Given the diversity and controversy described earlier, what is the basis of the family resemblance? At a fundamental level, despite differences in technique and concept, diverse forms of CBT agree that the overall project is one of developing a form of psychotherapy based upon scientific principles and validated via the scientific method of experimentation. The basic notion is embodied to such an extent in classical Beckian CBT that the metaphor offered to the client is one of 'learning to become one's own therapist by adopting the scientific-experimental method to one's beliefs' (Westbrook et al., 2017). However, some of the controversies that exist in the field are expressive of basic philosophical differences in how the activity of 'science' should be understood, carried out and evaluated.

Consider the still unresolved question of the relationship between thoughts, emotions and behaviours highlighted above. While classical Beckian CBT maintains that the mediating factor in achieving beneficial outcomes is cognitive change, and that it makes sense to differentiate cognition from emotion and behaviour, acceptance and commitment therapy (ACT) asserts that beneficial outcomes are more likely when both the therapist and client step away from direct attempts at achieving cognitive change and instead focus on the possibility of acceptance. Furthermore, ACT disputes that cognitions can be separable from behaviour in any meaningful sense. They also cannot be regarded as being causal. More recently, additional controversy has arisen from the fact that both groups of researchers and practitioners claim empirical support for their positions, in contrast to those of other CBT perspectives, from the very same experimental research findings. This dilemma has led some to propose that different versions of CBT do not simply represent a range of opposing techniques and concepts but are in fact expressions of entirely different philosophical worldviews (Herbert et al., 2016).

Contemporary practitioners of CBT, and new practitioners in particular, are thus faced with a bewildering range of theories and strategies and, at times, competing propositions of how best to be of service to their clients. The forms of CBT favoured in government-funded services, however, have tended to strongly emphasise the delivery of the so-called second wave 'disorder specific' and manualised interventions. This has led to criticism from outside CBT (House & Lowenthal, 2008) that CBT is in essence a quasi-medical approach, reliant upon diagnostic classification, that attempts to 'remove symptoms' and 'adjust' clients to the prevailing socio-political ideology of neo-liberalism. The apparent success of the CBT for x approach covers over the fact that, in the history of cognitive and behavioural therapies, there has always been a strong tradition of challenging the necessity, usefulness, reliability and validity of psychiatric classification as a basis for providing therapy. This challenge has arisen again as erstwhile opponents in the behaviour-versus-cognition wars have called a truce and proposed that further developments in CBT may be dependent on moving away from any reliance or endorsement of psychiatric classification of mental disease entities, and moving towards an approach that emphasises the identification of key processes, such as attentional fixation, cognitive fusion, rumination, avoidance and negative affect that are common across different forms of psychological suffering. These researchers suggest (Hayes & Hoffmann, 2018, p. 15): 'This approach might counter the drawback of training clinicians in disorder-specific CBT protocols, which often leads to an oversimplification of human suffering, inflexibility on the part of the clinician and low adherence to evidence-based practices'. Furthermore, these authors suggest that an approach based upon the identification of key psychological processes and upon the development of evidence-based ways of working with these processes that rely upon the intensive exploration of the experience and context of the unique client-an approach that abandons the psychiatric-medical system of diagnosis-may lead to the eventual 'death' of CBT as a distinct approach; Hayes and Hoffmann (2018, p. 436) state:

This will not occur because all evidence-based methods will be shown to emerge from CBT. Rather, as CBT reorients towards issues that were previously the focus of other therapy traditions, there will be fewer and fewer reasons to distinguish CBT from analytic, existential, humanistic, or systemic work.

These authors, who identify themselves as leaders of both the cognitive and contextual behavioural science wings of contemporary CBT, thus appear to re-open the possibility of dialogue with alternative perspectives, including that of existential therapy.

Existential Therapy and CBT: An Interrupted and Incomplete Dialogue

At first glance, existential therapy seems the most unlikely of partners in any dialogue that has even the faintest hope of identifying areas of convergence and agreement with CBT. Nevertheless, the suggestion that various forms of CBT and existential phenomenology may have points in common, and may potentially enrich and challenge each other, is by no means a new one. As early as 1963, a symposium considering the relative strengths and limitations of behaviourism and phenomenology was held at Rice University (Day, 1969). In addition, the possibility that phenomenology and radical behaviourism, particularly the psychology of B.F. Skinner, share points of contact has been noted numerous times in the literature (e.g. Butcher, 1984; Fallon, 1992). Clark et al. (1999), writing from a more cognitive perspective, suggested that the philosophical perspective most consistent with the practice of CBT was existential phenomenology. In fact, as will be discussed further, Beck et al. (1979), in their seminal text on cognitive therapy for depression, acknowledge Ludwig Binswanger, an early proponent of existential therapy, as an inspiration for the development of...