Semihypnotic trance induced by one of several "awareness spectrum" narcotics in which the petit betrayals of deliberate falsehood are apparent to the truthtrance observer. (note: "awareness spectrum" narcotics are frequently fatal except to desensitized individuals capable of transforming the poison-configuration within their own bodies.)

A Truthsayer is One of an elect group of Reverend Mothers adept in the ways of truthtrance and able to discern and identify falsehood, deceit, and insincerity but also anyone who can detect truth when it is being told. The ability to see truth was also seen as a gift that some individuals were born with. Paul Atreides was identified as one such individual by the RM Gaius Helen Mohiam when she first met him on Caladan in 10191 AG.

The Truthsayers were to represent the spiritual school of the Sisters, acting as their heralds and as the guardians of the Sacred Way to Truth. These holy Reverend Mother Truthsayers were responsible for the restoration and preservation of those qualities, characteristics, and objectives identified with the human cause. The Nine were to investigate the nature of humankind continuously, its customs, practices, societies, passions, weaknesses, and instincts, as well as to assess its cosmic destiny. To realize so monumental a task, each member of the Council of Nine had to have concentrated imagination, audacious conception, savage intention, unbridled psychic sensitivity, and iron will, qualifications then tempered and honed to suit the objectives of the Council.

The special abilities of the Truthsayer supposedly were inherited through Mother Jehanne from the Great Mother (who was reputed to know all things in themselves). Accordingly, only a Truthsayer could properly identify those qualities in one of her Sisters, since the art of divining falsehood was vouchsafed only to a handful of the Elect Reverend Mothers at any one time, led by the Holy Mother, Head of the Cogita Vera Council.

The call to become one of the Council was a heavy burden of responsibility, placing inordinate demands physically, mentally, and spiritually on a woman.