In the introductory chapter we lay the groundwork for the organization of the argumentation we deploy in the book, comprising a philosophical, a theoretical and a methodological part. The philosophical part concerns how singular causality can become the basis for seeking mechanism-based explanations through biographical research. The theoretical part focuses on how the concept of lived experience can be re-construed through the intermingling of reconstructive biographical research with critical realism. Finally, the methodological part revolves around the implementation of this intermingling in research practice. We analyze the reasons why, to date, qualitative researchers have remained indifferent to combining causal thinking with biographical research and we provide reasons why this must be changed.