There is a great need to better understand how teachers develop their knowledge and practices to better deal with the problem-solving situations they confront in their teaching life. Research on teacher thinking and problem solving has been based on a fundamental distinction between teachers’ beliefs and knowledge, and how teachers’ intuitive beliefs about learning may influence the way they interpret current information about learning and teaching. In this chapter, I discuss some similarities among the constructs used in educational psychology to describe the beliefs and knowledge of teachers, and those used in cognitive science and science education to describe students’ na¯ve and scientific theories. I proceed to show how findings in the area of student learning can be used to further our knowledge about teacher cognition, with a focus on how to deal with the issue of fragmented and inconsistent knowledge.