Book review: Causality Rules, Second Edition Vladimir Pascalutsa | Review by Christian Brosseau Causality is the relationship between a cause and its effect: an effect cannot occur before its cause. This concept is usually found in optics and electromagnetism as well as in Einstein’s theories of special and general relativity. This book is pleasant and contains careful discussions of a large number of topics dealing with the multifaceted aspects of causality such as Kramers-Krönig relations and sum rules. The book includes many pedagogical examples such as light-by-light scattering, nonlinear optics, and dispersion of rays in cosmic microwave background. Its target audience includes undergraduate and graduate students of optics, particle physics and astrophysics. #Causality #optics #electromagnetism #Einstein #light #optics #physis #astrophysics