A term coined by Charles Richet meaning a hidden sensibility, a perception of things by a mechanism unknown to us of which we are cognizant only of its effects. It indicated an all-inclusive psychic sense which comes into action by some mysterious external vibrations which Richet termed the "vibrations of reality," the so-called sixth sense. It includes clairvoyance, premonition, monition, psychometry, dowsing, and telepathy, for Richet believed that among the unknown vibrations that bring cryptesthesia into action, human thought is one that can most easily be transmitted.
He argued that telepathy as a hypothesis comes before cryptesthesia, since the reception of thought vibrations implies a new faculty. Psychometry and dowsing disclose knowledge of facts, so Richet classified them as pragmatic cryptesthesia.
The theory of cryptesthesia as a human faculty aimed at bar-ring the spirit hypothesis. It did so at the price of investing the living with flashes of omniscience.
With the establishment of parapsychology as the dominant school within psychical research, the term psi has largely superseded cryptesthesia as an overall term for the psychic faculty.