The metapsychological points of view were designed by Freud, using the vocabulary of the science of his time, to provide a

model of the mental apparatus based on the data of conflict. This model, like other primitive scientific models, was based upon metaphor. One of those metaphors was a quantification concept; in the absence of any specific thing to measure, it presented a niche in the structure for future dimensional quantification; moreover, developmental issues of structure formation may require further quantitative concepts. The economic metaphors ("displaceable quantity") serve some usefulness in the model of personal history in which events of the past achieve significance in the present.