William James defined psychology as "the science of mental life" and the psychologist/physicist William Stephenson used Newton's Fifth Rule of science to formulate a measurement technique for realizing this goal. In Part III of the "Two Sciences... " essays we use a Q methodology experiment with a single individual to exemplify the measurement of self-referential verbal behavior. This intensive analysis experiment is used to showcase Newton's first four rules for achieving objective science and Stephenson's actualization of Newton's complementary Fifth Rule for achieving subjective science. Viewed in this way objectivity and subjectivity are revealed as mutually exclusive and inter-dependent - an essential worldview for a quantum psychological science.