The essential openness of interpretation, which aims at understanding, may be contrasted with the aim of closure (logical, causal, teleological or genetic) between explanans and explanandum, which is usually considered the aim of explanation - defining, analysing and modelling entities and processes held to be the reason for what is observed of the object of interest. The contrast between explanation and understanding has been taken as a dichotomy or dualism referring to the appropriate aims of the social and natural sciences respectively.