This volume constitutes a special issue of the Michigan Mathematical Journal dedicated to William Fulton on the occasion of his 60th birthday. Attesting to the breadth of his contributions, the volume contains 30 papers on a wide range of topics centered in algebraic geometry, representation theory, and commutative algebra.

"Examining a topic that has been the subject of more than 300 articles since it was first conceived nearly 20 years ago, this monograph describes for the first time in one volume the basic theory and multitude of applications in the study of differential subordinations."