There is nothing so practical as a good theory. ~Kurt Lewin (1951) Activity Based Intervention (ABI) is approach used in early childhood programs to address the special needs of young and their families. Bricker and others have described ABI as a child-directed and naturalistic teaching strategy occurring in a context that is typical for young children, like their homes and community settings such as a preschool classroom (Bricker & Woods Cripe, 1992; Bricker with Pretti-Frontczak, & McComas, 1998; Pretti- Frontczak & Bricker, 2004). ABI addresses the developmental and educational goals of young by encouraging child participation in meaningful daily activities using behavioral learning principles. Four elements of ABI are: * development of goals for that are functional and can be generalized across settings, events, people, and time; * implementation of activities to address goals that are child-directed, routine, and planned; * child experiences consequences and timely feedback that are integral to the intervention; and * child experiences a variety of learning opportunities to address their goals. The practice of ABI is based on a theoretical framework that has been evolving since the 1970s. In order to apply ABI effectively, it is necessary to have understanding of the underlying theory that has influenced practice. Core concepts are grounded in theory. Leonardo DaVinci is reported to have said, He who loves practice without theory is like the sailor who boards ship without a rudder and compass and never knows where he may cast. Similar to DaVinci's sailor, Interventionists need a theoretical base to guide quality practice. The purpose of this paper is to highlight the theoretical foundation of ABI, and then describe examples of theory-driven ABI practice. Theoretical Perspectives What is a theory? Sroufe, Cooper, and DeHart (1992) define theory as, an organized set of proposals about how things operate. It is attempt to summarize current observations in light of past observations and to predict future ones (p. 14). Theory is NOT a list of references, data, opinion, list of variables or constructs, diagrams, or hypotheses (Sutton & Staw, 1995). It is often difficult to reach consensus on what constitutes a theoretical contribution (DiMaggio, 1995; Whetten, 1989). Berk (1999) points out that a theory must be testable, and offer a structure for cataloging our observations. She further explains, Theories that are verified by research often serve as a sound basis for practical action. Once a theory helps us understand development, we are in a much better position to know what to do in our efforts to improve the welfare and treatment of children (Berk, 1999, p. 5). Currently, neither the fields of education nor psychology have a global theory that is capable of addressing all aspects of human behavior. Existing theories tend to focus on different aspects of child development and learning (e.g., social and cognitive). Therefore it is necessary to draw from multiple theories to assist in explaining the complexity of human behavior. One theory alone cannot explain all the mysteries and phenomena associated with the human condition. ABI has eight theoretical perspectives (Bricker & Woods Cripe, 1992; Bricker et al., 1998; Pretti-Frontczak & Bricker, 2004), which include: (a) cognitive, (b) developmental, (c) ecological, (d) learning, (e) situated cognitive learning, (f) social learning, (g) sociohistorical, and (h) transactional. What follows is a brief explanation of each theory and how the theoretical perspective applies to ABI. Cognitive The research and writings of the Swiss theorist Jean Piaget have influenced the ABI approach. His background in biology, and observations of his own children, lead way to his understanding of how human beings develop across the life span. …