Research methodology : in the life behavioural and social sciences Historical remarks Graphical representation Meta data: well defined models of data sets Experimental design Clinical trials Cross sectional research Longitudinal analysis Measurement models Graphical modelling Structural equation modelling Graphs causality and structural equation models Meta analysis Discussion Comments David J. Hand On models and theories Jan B. Hoeksma Methodology in practice and research thereupon Dirk J. Kuik Comment: a unified theory P. Dick Bezemer Comments on causal explanation Judea Pearl Additional comments Herman J. Ad(c)·r A rejoinder Gideon J. Mellenbergh