ESP and Attempts to Explain It
It will be convenient to begin with some definitions offered by Mundle (1967). ESP, or extrasensory perception, is 'the acquisition of information without the use of any human sense organs'. The main subspecies of ESP are telepathy, in which 'the information originates from the mind of another person', clairvoyance, in whieh 'the information originates from physical objects', and precognition, in whieh 'the information is about and originates trom future events'. We mayaiso note the terms retrocognition-ESP in which the information is about and originates from past events, and psychokinesis (PK)-the direct inftuence of mental events. on physieal events external to the agent's body. These definitions are, as M undle points out, not altogether satisfactory; but for immediate purposes they will suffice.