Like all films with a fantastical element, Inside Out establishes its own rules. In this case, it sets out that people’s behaviour is governed by their emotions and specifically: Joy, Sadness, Fear, Hate and Disgust. Which raises the first question: why these emotions?Why have fear but not courage? Why have hate but not love? The answer is obvious enough - that for the plot to work, Riley’s character must face a crisis if Joy is lost. For her to be this mentally fragile, she must have mainly negative emotions, which are usually kept in check by Joy.