William Perry worked with college students in an effort to explain how they learn. His stages of intellectual and moral development can be divided into four categories:

1. Dualism - students see things in black and white terms (right/wrong, good/bad, pass/fail, etc.)

2. Multiplicity - students accept a variety of opinions but don't know yet how to assess the validity of these ideas

3. Relativism - abstract thinking leading to a rejection of easy absolutes - students can now assess the validity of different ideas; though teachers are respected for their knowledge, they can still be questioned

4. Commitment - students take personal responsibility for dealing with the right/wrong dichotomy