This article starts from the assumption that the learning of a foreign language is too complex to be explained though one learning theory. In an attempt to solve this problem, a transdisciplinary approach is proposed, starting from complex theories and including Chaos Theory, Complex Thinking, and Activity Theory. The ideas of Nicolescu on transdisciplinarity is summarized, using a evolutionary perspective of science through the stages of disciplinarity, multidisciplinarity, interdisciplinarity, and transdisciplinarity. It is finally suggested, as an example of the transdisciplinary approach, that research be guided from the problem to the theory, and not the other way around, as it has usually been done.