ABSTRACT
This chapter focuses on the key principles that have been influential in shaping the theory and practice of Acceptance & Commitment Therapy (ACT) as a psychological intervention. It introduces practitioners to Relational Frame Theory (RFT); a behavioural account of language that has been a significant theoretical driver of the development of ACT. One might consider RFT and ACT to be like siblings that have grown up together and influenced each other’s growth and development. The chapter discusses the psychological flexibility concept itself, as well as the several core processes that contribute to it. In the service of assisting practitioners, the reader, to locate their understanding of ACT within the wider behavioural tradition, this part will firstly offer a kind of ‘Behaviourism 101’.
