The fascination with dreams has continued through the various phases of human history. The

re is reason to believe that the earliest societies may have considered dreaming as a voyage of the soul, a separation but quite definite being of the person. This, indeed, is how many primitive societies think of dreams today. More advanced societies have often thought of dreams as containing messages from the gods. This was one of the views held in ancient Egypt and Greece. While sleep has been considered an appropriate object of scientific study, dreaming has usually been considered rather a subject for fairy-tales and legends, and a plaything for philosophers. Even when Europeans started making progress in the physical and biological sciences, they dismissed dreaming as a proper scientific object because dreams were chiefly incomprehensible products of an inefficient, poorly oxygenated brain. In the nineteenth century, however, at least some medical men and scientists took dreaming more seriously and noted that dreams were perhaps the psychoses of madness of the normal man, during which strange and usually hidden thoughts appeared. This was in a sense a rediscovery of an old idea, already mentioned in Republic. Freud accepted this idea, and used his insight into dreaming to propose a complete theoretical outline for the organization of thought, involving primary processes and secondary process thinking. Freud was so impressed with the possibilities offered by the study of dreams for understanding mental life that he spoke of the dream as royal road to the un conscious.

However, Freud and the psychiatrists who followed him considered dreaming from feeling and probably instantaneous phenomenon. The prevalent view was that either dreaming took place during the moment of awaking, or, on the other hand, that dreaming occurred constantly but was only very occasionally and haphazardly "sampled" by consciousness. In either ease, the various properties of dreaming were explained on the basis of the properties of the solid underlying state of sleep.

A great deal of recent work completely contradicts this formulation indicating that dreaming is associated with an entire biological state of its own, state in many ways as different from ordinary sleep as it is different from waking. This biological state, or the D-state, has been found to occur in all mammalian species studied, as well as in people. It occurs at times when the psychological experience of dreaming is unlikely; for instance, in the newborn child, and the newborn cat. Recently a new field of inquiry has been developed by Aserinksy, Kleitman and other workers in the physiological, biological, and chemical sciences. This new field is the biology of dreaming, which sometimes has a focus far removed from the psychology of the dream. Through modem scientists' joint effort, mysteries of dreaming may soon be unlocked.

The author considers our understanding of dreaming someday ______.

A．imaginary

B．likely

C．suspicious

D．inevitable