The mistakes children make in mathematics are usually not just 'mistakes' - they are often intelligent generalizations from previous learning. Following several decades of academic study of such mistakes, the phrase 'errors and misconceptions' has recently entered the vocabulary of mathematics teacher education and has become prominent in the curriculum for initial teacher education.

The popular view of children's errors and misconceptions is that they should be corrected as soon as possible. The authors contest this, perceiving them as potential windows into children's mathematics. Errors...