Fits, Passions and Paroxysms: Physics, Method and Chemistry and Newton's Theories of Colored Bodies and Fits of Easy ReflectionBuilding upon his pioneering investigation of the colours of thin films, Isaac Newton developed two influential theories, one on the structure of matter, explaining the colours of bodies and the other on fits, describing the periodicity of light. Professor Alan Shapiro, editor of The Optical Papers of Isaac Newton, recounts the development of these theories based on his study of Newton's unpublished manuscripts and analyses their experimental