Since 1985 the Colgate University Department of Physics and Astronomy has been reshaping the first term of introductory calculus‐level physics to answer the question: ‘‘Why do we believe in atoms and the properties ascribed to them?’’ This paper describes the new course, its 400‐page text, its ten laboratories, its six computer exercises, and how these work together successfully to serve several purposes: For those students who do not continue on with any more physics, it is a good introduction to physics; for the many students whose quantitative skills need enhancing, it provides a better chance to improve those skills than traditional introductory physics; by its emphasis on wave‐particle duality and mass‐energy equivalence, the course introduces students to important quantum and relativistic ideas that are fundamental to most of what contemporary physicists actually do. We also extract from our reform efforts some lessons useful to anyone undertaking to change introductory physics.