'Chemistry is the science which treats of the intra-atomic or the intra-molecular changes which material things undergo under various influences. Mental is defined as of or appertaining to the mind, including intellect, feeling, and will, or the entire rational nature. Science is knowledge gained and verified by exact observation and correct thinking. Mental chemistry is, therefore, the science which treats of the changes which material conditions undergo through the operations of the mind, verified by exact observation and correct thinking.' -Charles F. Haanel