Philosophy of Technology Assessment: Problems of Quantification and Prediction. Technology Assessment (TA) as an interdiscipline project to assist decision-making in the area of technology politics is well-established. A critical analysis based on the constructive philosophy of science, however, uncovers several deficiencies of the philosophical foundation of TA. Especially the fundamental differences between natural and social sciences are neglected by the TA, for example by treating normative problems of decision-making with descriptive techniques of quantification and prediction. It is shown that in TA the philosophical limitations for quantifications and predictions — based on elements of acting theory and a reflection on the nature of descriptive and normative propositions — are ignored. Consequently, a revision of the foundations of technology assessment is suggested.