The philosophy of this best-selling introductory text is to emphasize communicative proficiency. Based on the Natural Approach, the text stresses the use of activities in a natural and spontaneous classroom atmosphere. In this comprehension-based approach, the development of receptive skills listening and reading precedes and forms the basis for the development of the productive skills speaking and writing. "Dos mundos" is designed so that class time can be devoted to exposing students to Spanish through the abundant activities and readings in the text, allowing the grammar explanations and exercises to be studied outside of class.