AbstractThe measurement of psychological states requires an entirely different technology from the classical personality inventory assessments of psychological traits. Since the internal and external conditions of life change constantly measurements of psychological states must reflect such change. Differences in the requirements of state vs. trait measurement are discussed. Problems of naming, labelling, describing, defining, and interpretation are discussed in relation to psychological theory. Questions of item and factor homogeneity vs. heterogeneity, factor scale length and factor composition across occasions and times were investigated in pilot studies connected with the standardization of the Intergration Level Test Series. Finally, important questions are raised about deductive clinical reasoning and the use of factorial results to validate psychological theories.