This chapter returns to a long-standing issue in in language and identity research based on life story interviews - the need for theoretical and methodological rigour (Pavlenko, 2007). It begins with background: first a brief discussion of identity that highlights those aspects of the construct that later come to the fore, and second, presentation of a version of positioning theory (PT) recently developed by the author (Block, 2017). This version draws on the original PT model developed by Rom Harré and his associates but importantly, it expands on this model with the addition of constructs taken from sociolinguistics, sociology and social theory, including authenticity and authentication (Bucholtz, 2003), belonging (Guibernau, 2013), field and habitus (Bourdieu, 1993, 2000), discourse formations and gaze (Foucault, 1989, 2003) and resistance (Seymour, 2006). The second half of the chapter examines an excerpt from an interview with an English-medium instruction lecturer, drawing on constructs developed in the first part. The aim is to show how the version of PT presented can lead to a detailed and nuanced interpretation of the construction of identity, turn by turn, in an interaction.