This paper indicates underlying philosophic assumptions which are compatible with the behavior analysis approach to child development. Four issues taken into consideration are (a) biology and environment, (b) structure and function, (c) traits and situations, and (d) mechanistic and organismic approaches to development. The following ideas represent in part the behavior analysis position on the issues discussed. Physiological structure and functioning influence the behavioral structure of a child's interactions with the environment and determine the broad behavioral processes which occur within child-environment interactions. Structural and functional analyses are complementary. The structure and function of child-environment interactions are mutually determined by development. Stimulus functions and response functions develop together and are defined with respect to one another. It is impossible to view stimulus functions as having more control over behavior than response functions. Organismic and mechanistic world hypotheses should not be viewed as necessarily antagonistic to one another. In summary, behavior analysis need not be exclusively environmentalistic, solely functionally oriented, situationist, or mechanistic. It is emphasized that philosophic assumptions influence the work of every scientist and are too important to be ignored. (Author/RH)