ABSTRACT
A. What is a Stimulus? Now that we have set the stage for our discussion by placing the scientific and technical aspects of sensory psychophysiology in their appropriate philosophical context, we can begin our journey up the ascending pathways. We must start, however, with some nonphysiological facts, for it is always some inorganic aspect of the extern al world of physical energies that is the precursor for each sensory response. Though sense organs in many cases do respond without the presence of some identifiable external physical action, we shall not be concerned with such "spontaneous" or "persistent" activity for the moment. Rather, in this chapter, we shall try to provide the necessary foundation material so that the reader will be able to interpret the metrics used for the specification of stimuli.
