This article discusses the concept of 'validity' in qualitative and quantitative research, arguing that 'validity' is not a single, fixed or universal concept, but rather a contingent construct, grounded in the processes and intentions of particular research methodologies and projects. The author explores the challenges in defining 'validity' in both research approaches and highlights the differences and similarities in how validity is claimed by quantitative and qualitative researchers. It is argued that an understanding of the nature of 'truth' is central to any theorisation of 'validity', as the affiliations of methodologies concerning truth generate varying notions of validity. The article reviews various definitions of 'validity' and 'reliability', noting that they are often confused and vary significantly. It discusses different types of validity, including descriptive, interpretive, theoretical, generalisability, and evaluative validity, and how they are applied in qualitative and quantitative research. The author argues that validity is not a unitary concept and that the methods used to achieve validity differ between qualitative and quantitative research. In qualitative research, validity is often related to the representation of actors, the purposes of the research, and the appropriateness of the processes involved, rather than to the accuracy of the findings. The article also addresses the issue of who the research is valid for and the ethical implications of making claims to truth. It highlights the importance of understanding the nature of truth and how it is constructed within different research methodologies. The author argues that validity is not a feature of a particular methodology, process, or test, but rather depends on how representative the description is and how justifiable the findings are. The article concludes that understanding is more pertinent to qualitative research than validity, and that qualitative research sets itself up for failure when it attempts to follow the established procedures of quantitative research.This article discusses the concept of 'validity' in qualitative and quantitative research, arguing that 'validity' is not a single, fixed or universal concept, but rather a contingent construct, grounded in the processes and intentions of particular research methodologies and projects. The author explores the challenges in defining 'validity' in both research approaches and highlights the differences and similarities in how validity is claimed by quantitative and qualitative researchers. It is argued that an understanding of the nature of 'truth' is central to any theorisation of 'validity', as the affiliations of methodologies concerning truth generate varying notions of validity. The article reviews various definitions of 'validity' and 'reliability', noting that they are often confused and vary significantly. It discusses different types of validity, including descriptive, interpretive, theoretical, generalisability, and evaluative validity, and how they are applied in qualitative and quantitative research. The author argues that validity is not a unitary concept and that the methods used to achieve validity differ between qualitative and quantitative research. In qualitative research, validity is often related to the representation of actors, the purposes of the research, and the appropriateness of the processes involved, rather than to the accuracy of the findings. The article also addresses the issue of who the research is valid for and the ethical implications of making claims to truth. It highlights the importance of understanding the nature of truth and how it is constructed within different research methodologies. The author argues that validity is not a feature of a particular methodology, process, or test, but rather depends on how representative the description is and how justifiable the findings are. The article concludes that understanding is more pertinent to qualitative research than validity, and that qualitative research sets itself up for failure when it attempts to follow the established procedures of quantitative research.