Constructing knowledge is an extremely active endeavor on the part of the learner(Baroody 1987. Cobb, 1988. von Glasersfeld, 1990). To construct and understand a new idea in volves making connections between old ideas and new ones. "How does this fit with what already know?" "How can understand this in the face of my current understanding of this idea?" Mathematical ideas cannot be"poured into" a passive learner. Children must be mentally active for learning to take place. In classrooms, children must be encouraged to wrestle with new ideas, to work at fitting them into existing networks, and to challenge their own ideas and those of others. Put sim ply, constructing knowledge requires rdlective thought actively thinking about or mentally working on an idea Networks of ideas that presently exist in the learners mind determine how an idea might be constructed These integrated networks, frequently referred to as cognitive schemas. are both the product of constructing knowledge and the tools with which new knowledge is constructed The more connections with the existing network of ideas, the better the new ideas are understood. As learning occurs, the networks are re arranged, added to, or otherwise modified. When there is active, reflective thought, schemas are constantly being modified or changed so that ideas fit better with what is known