Theoretical and Philosophical Foundations of DBT. A central dialectic between acceptance and change lies at the heart of DBT. In developing DBT, Linehan initially attempted to apply behavioural theory and change strategies to clients presenting with BPD and suicidal behaviour. She experienced several difficulties in these early stages of treatment development. Clients' were frequently non-collaborative in-session, did not practise agreed homework assignments and often did not return for subsequent treatment sessions at all. Linehan hypothesised that these 'therapy-interfering behaviours' arose because the clients experienced the strong focus on changing emotions, thoughts and behaviours as invalidating. Indeed, as clients often believe they are incapable of change, the whole notion of a treatment based on change is fundamentally invalidating. In response to these concerns, she searched for a philosophy / theoretical approach that strongly emphasised acceptance. Zen principles and practise underpin the acceptance-based components of DBT. To house these two contrasting approaches, Linehan uses dialectical philosophy. The following sections of this paper discuss these three foundations of the treatment in more detail.