Few reports about methods of evaluating quality of life (QoL) among the thousands published since medical interest in the subject slowly began nearly 40 years ago are based upon theory. This paper, prepared in response to a request to furnish an exception (Meadows KA. Introduction to an Advanced Seminar: Assessing Health-Related Quality of Life. What can the Cognitive Sciences Contribute? Hull University, October 9, 2000) describes the origins of the Schedule for the Evaluation of Individual Quality of Life (SEIQoL). This derives its cognitive aspects from theoretical studies of perception by Egon Brunswik, their extension to Social Judgment Theory (SJT) by Kenneth Hammond and the application of these ideas to QoL by the present authors and their colleagues.