Causality in qualitative and quantitative research

We are flooded with a wave of writings on causality in the social sciences during the last decades. The same holds for the relationship between quantitative and qualitative research in the social sciences. An enormous amount of texts appears on (causality in) qualitative research, mostly in a controversy with quantitative research. These writings induced us to develop the thesis of "unity in diversity", i.e., that there is no difference "in principle" between causality in qualitative and quantitative research, because both are supported by what I will call an "experimental logic". In developing this thesis a plea is being made for going back to the sources. A historical overview of theories of causality is presented, which develops into two prominent views: INUS-causation and causal realism. A historical framework is also outlined for the opposition between quantitative and qualitative research, in which French positivism and British empiricism are opposed to German neo-kantianism and neo-hegelianism. After having developed the thesis of "unity in diversity" for this historical framework, the same is being done for the recent literature: "mixed methods research", the book DSI of KKV, the reactions of David Collier and "QCA" of Charles Ragin. At the end the question of small-n research and the case n = 1 is examined.