 For one thing, almost all studies aimed at elucidating reaction mechanisms rely on indirect techniques. Ideally, elucidating a reaction mechanism would be like doing experiments in biomechanics. Slow motion video could give direct information about the movement of parts and how these movements give rise to the motion of the whole. But we have nothing like a video camera for chemical reactions. Instead, after an experimental determination of the reaction products and possible isolation of stable intermediate species, chemists rely on measurements of reaction rates in differing conditions, spectroscopy, and isotopic labeling, among other techniques. These techniques help eliminate candidate reaction mechanisms, but do not themselves directly suggest new ones. This emphasis on eliminating possibilities has led some chemists to endorse a Popperian, falsificationist analysis of reaction mechanism elucidation (e.g., Carpenter 1984).