Models and metaphors play an important role in the human sciences. In a metaphor some domain of reality, such as human development, is associated with another domain of reality. By this process of association some aspects of the first domain are emphasized and others are neglected. Models and metaphors, which are often used unconsciously, implicitly determine research by directing the questions asked and the methods chosen for answering them. In scientific inquiry different models and metaphors may be used at the same time. Nevertheless it is important to distinguish the models, to describe them separately, and to clarify their various aspects. By doing so philosophy can make explicit the presuppositions of scientific research.