A plain-language glossary of the terms you will meet when reading about closed-eye vision, intuition and the pineal gland. It has 41 entries in four groups, with links to the articles in our Journal. Seeing Beyond Matter does not describe any brain mechanism for its kit.
Perception and experience
Closed-eye vision
The name people give to perceiving colors, shapes, numbers or letters while the eyes are covered by a lightproof mask. Families around the world describe it. See the complete guide to closed-eye vision and a parent’s introduction to closed-eye vision.
Eyeless sight
The English title of Jules Romains’ 1924 book (translated by C. K. Ogden), and a general name for perceiving without the eyes. See paroptic vision: what the term means and the library of rarely read sources, and compare extra-retinal vision.
Extra-retinal vision (paroptic sense)
Terms used by the French writer Jules Romains in 1920 (vision extra-rétinienne and sens paroptique) for a perception he believed to be independent of the retina. See paroptic vision: what the term means, and compare eyeless sight.
Blindfold reading
Reading, or naming colors and objects, while the eyes are covered. It appears in stage acts and in accounts of closed-eye vision. A truly lightproof mask is the starting point for any serious practice.
Mindsight
A popular name, used in online communities and training programs, for perceiving while the eyes are covered. Psychology uses the same word for a different idea, so it helps to check the context. See the complete guide to closed-eye vision, and compare closed-eye vision.
Closed-eye visuals
Colors, lights, patterns and moving shapes that many people see with their eyes closed, especially in the dark. A common experience, sometimes called “prisoner’s cinema”. It is related to phosphenes and hypnagogic imagery.
Eigengrau
From the German for “intrinsic gray”. The uniform dark gray that most people see with their eyes closed in a dark room, instead of true black. It is a documented feature of the visual system, which is never completely silent. See what you see when you close your eyes, and compare phosphenes.
Phosphenes
Flashes or patterns of light seen without light entering the eye, caused for example by pressure on the eye or spontaneous activity in the visual system. A documented, everyday experience.
Hypnagogic imagery
Vivid images that can appear while drifting into sleep. A documented experience of the inner world. The same experience on waking is called hypnopompic imagery.
Hypnopompic imagery
Vivid images that can appear while waking up, the counterpart of hypnagogic imagery. The term comes from Frederic Myers. See what you see when you close your eyes.
Mind’s eye
An everyday expression for the ability to picture things in the imagination. The phrase appears in Shakespeare’s Hamlet and is still used in psychology as a shorthand for mental imagery.
Mental imagery
The experience of picturing something in the mind without it being in front of you. People differ widely in how vivid it is, and psychologists often measure this with questionnaires such as the Vividness of Visual Imagery Questionnaire, introduced by David Marks in 1973. See also aphantasia and eidetic imagery.
Aphantasia
The term proposed in 2015 by Adam Zeman and colleagues for people who report little or no ability to form visual images at will. It is a documented variation in how people experience imagery, found in a small share of people. See aphantasia and closed eyes.
Eidetic imagery
Unusually vivid, detailed visual memories that seem to stay “in view” for a short time after the image is gone. Researchers in the 1920s, notably Erich Jaensch, described it mainly in children.
Synesthesia
A documented trait in which one sense triggers another, for example letters that appear colored or sounds that evoke colors. Studies suggest it affects a few percent of people, and it shows how rich and varied human perception can be.
Blindsight
A documented phenomenon, described from the 1970s in work associated with Lawrence Weiskrantz, in which people with damage to part of the visual system say they see nothing yet respond to some visual stimuli better than chance would predict. It concerns eyes-open vision after brain injury.
Ganzfeld effect
From the German for “entire field”. The experience that follows when the eyes see only an even, unstructured field of light or color, for example through halved translucent balls. People often report imagery and altered perception. Wolfgang Metzger described it in 1930, and it has also been used in parapsychology experiments.
Intuition
A judgment or sense of knowing that arrives without step-by-step reasoning. Psychologists such as Daniel Kahneman and Gary Klein have studied how quick, experience-based judgments work. Intuition is a documented subject of study and a theme that runs through the book Seeing Beyond Matter.
Related ideas and practices
Dermo-optical perception
The name given to 1960s accounts of perceiving colors through the fingertips, associated with reports about Rosa Kuleshova in the Soviet Union. See paroptic vision: what the term means for what the tests found.
Lightproof mask
A practice mask that blocks all light, especially around the nose, and rests on the face without pressing on the eyes. Practice begins in true darkness, which is why we describe how to check a mask in what to check in a training mask.
Midbrain activation
A commercial name for children’s programs that include blindfold exercises. Seeing Beyond Matter is a different, home-based offer and does not use the term to describe its kit. See our guide to courses, workshops and home kits, and the anatomy entry for the midbrain.
Extrasensory perception (ESP)
A term popularized by the parapsychologist J. B. Rhine in the 1930s for perceiving information without the known senses. See clairvoyance and remote viewing.
Clairvoyance
From the French for “clear seeing”. The ability, described in many traditions, to perceive objects or events beyond the reach of the ordinary senses, treated as a form of extrasensory perception.
Remote viewing
The name for perception of distant places or hidden targets. It is associated with experiments at the Stanford Research Institute in the 1970s and with a US government program later known as the Stargate Project, which ran until 1995.
The pineal gland and the body’s clock
Pineal gland
A small pine-cone-shaped gland near the center of the brain, roughly 7–8 mm long in humans. In 1958 a team led by Aaron Lerner isolated melatonin from it, giving it its first established function. See the history of the pineal gland.
Epithalamus
A small region at the rear of the brain’s central part (the diencephalon). It includes the pineal gland and a few other small structures, which is why the gland is described as sitting near the midline of the brain.
Brain sand (corpora arenacea)
Tiny calcium deposits that often form in the pineal gland in adults. They show up on X-ray images, which is why radiologists have long used the gland as a landmark.
Melatonin
A hormone made mostly in the pineal gland and produced mainly during the dark hours, which helps the body follow the rhythm of light and dark.
Circadian rhythm
The body’s roughly 24-hour cycle of rest and activity, driven by an internal clock and tuned by light and darkness. The word comes from the Latin for “about a day”. See melatonin and the suprachiasmatic nucleus.
Suprachiasmatic nucleus
A tiny region of the brain, in the hypothalamus just above where the optic nerves cross, that works as the body’s main internal clock. In mammals, information about light reaches the pineal gland by a relay that starts in the eyes and passes through this clock.
Midbrain
The uppermost part of the brainstem, containing structures involved in eye movements and in reflex responses to light and sound. “Midbrain activation” is a commercial name used by some programs for children; see midbrain activation. Seeing Beyond Matter does not say that its kit acts on the midbrain.
Parietal eye
A light-sensing “third eye” on top of the head in some reptiles, such as the tuatara and many lizards. It has a lens and a simplified retina. This is the biological meaning of “third eye”.
Opsin
A light-sensitive protein used by photoreceptor cells. The rod and cone cells of the human retina each use opsins, and related opsins occur in the parietal eyes of some reptiles. See lepidopsin.
Lepidopsin
An ancient light-sensing opsin gene reported in a 2025 study by Romero and de Souza in Genome Biology and Evolution. The authors found it in the tuatara and most lizard groups and linked it to the parietal eye. See the paper.
Tuatara
A reptile native to New Zealand, one of the only living members of an ancient order of reptiles, with one of the most visible parietal eyes. See parietal eye.
History and tradition
Third eye (spiritual)
A spiritual and symbolic idea found in many traditions, separate from the parietal eye in reptiles. In Indian traditions it is associated with the ajna (brow) chakra and with insight. For many people it is a symbol of inner sight.
Ajna chakra
In Indian traditions, the energy center said to lie between the eyebrows, associated with insight and intuition.
Seat of the soul
The phrase René Descartes used for the pineal gland in the seventeenth century, as the point where he believed mind and body meet. It remains one of the best-known proposals in the philosophy of mind.
Pneuma
Greek for “breath”. In ancient Greek medicine, a vital substance thought to carry life and mental activity through the body. Herophilus is reported to have imagined the pineal gland controlling the flow of a mental pneuma between the brain’s chambers. See the history of the pineal gland.
Eye of Horus
An ancient Egyptian symbol of protection and prosperity. Some writers connect it to the pineal gland.
Theosophy
A spiritual movement founded in 1875, with Helena Blavatsky as its best-known writer. Her book The Secret Doctrine (1888) proposed that the pineal gland is the remnant of a literal third eye. It is a foundational text of the modern esoteric tradition.
Looking for the primary sources? See our library of rarely read sources.
This glossary is for general education and is not medical advice.