“Since Pawlow and his pupils have succeeded in causing the secretion of saliva in the dog by means of optic and acoustic signals, it no longer seems strange to us that what the philosopher terms an 'idea' is a process which can cause chemical changes in the body.” SciencePhilosopherChemistryIdeaPavlovIvan PavlovChemical ChangesClassical Conditioning Book:The Mechanistic Conception of Life Source: The Mechanistic Conception of Life