An interdisciplinary study in constitutional law means the study of constitutional law by means of another scientific approach rather than the traditional legal analysis. A critical point is the relationship between legal science and the interdisciplinary studies. In order to ascertain the relationship between these different kinds of knowledge, it is necessary to investigate the nature of legal knowledge. It is to assert that the true nature of legal science is doctrinal (dogmatic). However, it is necessary to specify that legal science is legal dogmatics and to justify why it is legal dogmatics. There are at least two relationships between these sciences. One is to integrate the outcomes of interdisciplinary studies into legal dogmatics. The other means the integration of doctrinal knowledge of law into, for example, social sciences. In order to find an entrance for social science into legal dogmatics, the construction of doctrinal knowledge must be decomposed. This can be achieved through the analysis of the forms of legal argumentation. Since the teleological argument, especially in the form of consequential argument, *Associate Professor, School of Law, Shih-Hsin University involves both normative and cognitive (empirical) elements, it is an appropriate place for the “integration”. There is also a third possible relationship between legal dogmatics and interdisciplinary studies: a non-integrative, critical one. Since legal dogmatics often makes use of common sense by interpreting the law, the insights offered by empirical sciences that are critical can be used to deconstruct legal science. Interdisciplinary studies can be contributive to challenge background assumptions of legal science that are often decisive in legal decision making. It is finally to argue that the constitutional theory could play an important role in the interdisciplinary studies because of its two-dimension character. For the constitutional theory is not only its relationship to the legal dogmatics, but also that to the empirical studies constitutive.