The title of this chapter is really a statement, with a question inscribed in it, and a double meaning at its heart. It seeks to both answer 'why is psychosocial theory critical?' and argue that psychosocial theory is critical, in the sense of challenging orthodoxy, and in the sense of urgent and necessity. The short answer that will be advanced here is this: without engaging with people as subject to unequal forms of social power, interwoven with individual, affective struggles and troubles, you cannot hope to understand the complexities of human existence, let alone human existence in which some people are clearly experiencing forms of social suffering. Psychosocial thinking insists that humans are understood as being constituted within social structures and personal internal landscapes. However, there is also a third fundamental element, which is that the experiencing, relational human subject is placed at the centre of the analysis. The knower and the known in terms of knowledge construction; the worker and the service user in social work, are both equally dynamically present and constitutive in all encounters, and this subjective interface is fundamental to the relationship. The human subject is at the core of psychosocial understanding. As I have commented previously: Within this paradigm the subject is understood as passionate, ambivalent and emotionally driven, existing outside (but defined within) the rational processes of language. Importantly, this is a social subject existing in a world of power relations and status hierarchies. Psychosocial theory is able to explicate the emotional experience which, in relation to all encounters, including social work, defines the nature of the real and fantasised self and other in a coconstructed relationship.