The 1882 paper by the mathematical physicist Gustav Robert Kirchhoff on diffraction theory is still being discussed to this day, but has never been translated into English. This volume contains the first English translation of the Kirchhoff treatise, as well as background and commentary on it. Included are a biographical introduction to Kirchhoff's life, an analysis of the reception to Kirchhoff's paper through the ages, a discussion on why Kirchhoff's theory manages to produce accurate predictions in spite of being "wrong", and views on the theory as well as its predecessor and subsequent developments. This anthology will make all English-speaking scientists, engineers, historians, and interested laymen aware of the great fecundity of Kirchhoff's thought and historical context.