A synopsis of the history of humanistic thought is provided as a basis for ideas which have emerged in psychotherapy theory since the nineteenth century, reflected in the philosophy of Emmanuel Levinas (1981, 1989). These ideas can be associated with the concept of loving kindness in psychotherapy and the central importance of feelings. The notion of the mind/body split in philosophy and medical science is discussed with reference to Descartes; this thinking later challenged by the development of affective neuroscience in the twentieth-century work of Damasio and Panksepp. The relevance of intersubjectivity to an understanding of attachment, relational attunement and mentalisation, as proposed by Fonagy, Gerhardt, Holmes and others, is discussed. This is applied to contemporary insights about mental illness as proposed by O'Keane (2021). A connection is made between the development of psychotherapy and a previous cultural heritage of thought within the world religions and ideas about ‘good’, as discussed by Black (2015) and McKenna (2002) and in the philosophical writing of Iris Murdoch. Concluding reflections on the role of loving kindness in psychotherapy bring the book to its conclusion.