Constructivism has been embraced by many in the field of instructional design and technology (IDT), but its advocates have struggled to move beyond theory to practice or to empirically demonstrate the effectiveness of their approach. As an alternative to constructivism, a new perspective emerging in psychology, known as functional contextualism, is presented. Like constructivism, functional contextualism also rejects objectivist epistemology, but provides a much more coherent philosophical basis on which to build an empirical science of learning and instruction. The philosophical worldview known as contextualism is reviewed to outline the similarities and differences between constructivism and functional contextualism, and the key characteristics of functional contextualism and the science it supports, behavior analysis, are described. Implications of functional contextualism for research and practice in IDT are then explored. (Contains 1 table.)