This thesis aims to develop new understanding of commercial qualitative research, informed primarily by thinking from complex responsive processes, social constructionism and the philosophy of social science, supported by approaches to validity and legitimacy which are epistemologically appropriate to this understanding. Commercial qualitative research has the over-riding aim of helping to guide the decision making of the commissioning client; its purpose - and the way in which it is evaluated- is, essentially, determined by its perceived usefulness, rather than methodological considerations. Until recently there has been little interest within the qualitative industry in theory that informs practice. One result of this pragmatism is conflicting paradigms; an unquestioned 'positivism' sitting alongside-and intermingled with-a variety of 'interpretivist' approaches. This has resulted in much confusion, contradiction and, I believe, has stunted the development of the qualitative research industry. This thesis explores the meaning of 'inquiry'; how research 'data', and the processes of making sense of this 'data', can be understood within a commercial research context. I propose a view of qualitative research -'emergent inquiry' -which is not hidebound by research structure but which involves a process of joint and evolving sense-making. Starting from the premise that reliability and validity (as understood in their scientific application) are inappropriate ways of understanding 'emergent inquiry', I explore an understanding of legitimacy which, I believe, is more appropriate to the inquiry method that I have outlined. My intention, in this doctoral research, is to strengthen theoretical understanding, practice and legitimisation of commercial qualitative research practice. Through challenging taken for granted assumptions, I am attempting to contribute to the ongoing development of professional practice; highlighting a different understanding of qualitative practice-'emergent inquiry' -with appropriate legitimisation, rather than 'borrowing' legitimacy from an inappropriate 'positivist' epistemology.