Abstract

A simple theorem concerning the possibility of extrasensory perception (ESP) is offered. The theorem will be considered proved when the following conditions obtain: If a subject in a classical ESP experiment demonstrates fixed hit probabilities throughout the experiment, if he or she is not omniscient in any experimental situation, if he or she shows no preference for any alternative over the other alternatives in the guessing experiment, and if two-way guesses are just as reliable as direct guesses, then the subject will score in accordance with chance expectation.