This chapter proposes a definition for legal fiction. The problem of definition has divided scholars into multiple camps and held back progress. The definition proposed here is a compromise which seeks to preserve precision while covering the true range of fictitious devices. My definition is composed of two limbs: Hard Fiction and Soft Fiction. In developing this definition, I address a range of theoretical issues. I rebut arguments by Vaihinger and Kelsen that fictions do not exist. I discuss fictions from a linguistic perspective. I discuss the relationship between fictions and rules, and between fictions and counter-factuals. Also explored are contributions to the definitional debate by Fuller, Olivier, Ross, Chiassoni, Del Mar and earlier thinkers. The Chapter concludes with an application of the proposed definition in two case studies: the reasonable man and volenti non fit injuria. I argue the latter is a Soft Fiction and the former is not a fiction.

This chapter examines seven (alleged) modern fictions of private law: (i) the equitable maxim that equity treats as done that which ought to be done; (ii) estoppel; (iii) volenti non fit injuria; (iv) the single meaning rule in defamation; (v) the common intention constructive trust; (vi) remoteness in negligence; and (vii) reading down exclusion clauses. I establish whether each of these devices is a Hard Fiction, a Soft Fiction or no fiction (the Nature Classification). I classify each device in terms of the Effect Classification developed in Chapter One. If a device has been found to be a Hard or a Soft Fiction, I go on to consider whether it should be retained or abolished in favour of a specific alternative. These evaluations of individual fictions lead to general insights, which are used in the development of the Acceptance Test in Chapter Four.