The methodology utilized in much of the demand systems literature sets out to empirically test consumer theory in a logical positivist manner, but, inevitably the theory fails. If Karl Popper's agenda were consistently ~pplied the theory would cease to exist. Yet, economists are uneasy about destroying old dictums. So, empirically unsupported theoretical constraints are imposed on the data. If the theory is assumed to always hold ( an apriorist philosophy) then it should not be tested, and should be imposed from the beginning.