In this thesis, I propose that a perennial challenge for the actor is the embodiment and expression of emotion. Dramatists frequently place their characters in the most extreme circumstances imaginable, demanding a full-blooded response from the actor. But emotions are not in our conscious control. What is the actor to do? To illuminate this demanding artistic challenge, I develop a dual conceptual framework, drawing on emotion theory from the worlds of both acting and science, particularly psychology and neurology. How have practitioners and thinkers in these two fields accounted for the phenomenon of emotion and is there any convergence between their discoveries? I also examine how emotion has been approached in the UK conservatoire and focus on a selection of actor trainers who have placed this topic at the centre of their work: Stanislavsky, Vakhtangov, Lee Strasberg and Susana Bloch. The history of attempts to manipulate emotion for artistic purposes is a controversial one. At a time of unprecedented concern for student well-being and mental health, what might an ethical approach to ‘teaching emotion’ look like? What have we to learn from the science of the emotions and the training practice of the recent past? Can one be used to refresh the other and help reinvent past practice to create a new pedagogy of the emotions, fit for purpose in the 21st century?