We Hear All Types Of Sound In Our Brains

The hearing process also operates in a similar manner to the visual process. In other words, we hear sounds in our brains in the same way that we see the view of the outside world in our brains. The ear captures the sounds around us and delivers them to the middle ear. The middle ear amplifies the sound vibrations and delivers them to the inner ear. The inner ear transforms these sound vibrations into electric signals, on the basis of their frequency and intensity, and then transmits them to the brain. These messages in the brain are then sent to the hearing center where the sounds are interpreted. Therefore, the hearing process takes place in the hearing center in essentially the same way that the seeing process takes place in the seeing center.

The outer ear captures sound waves and delivers them to the middle ear. The middle ear amplifies these sounds and transmits them to the inner ear. The inner ear converts these sounds into electric signals on the basis of their intensity and frequency and then sends them to the brain.

The brain is soundproof as well as lightproof. Therefore, even if the noises we hear are loud, the insides of our brains are very quiet. However, in this silence, there is a consciousness that can interpret electrical signals as a melody that he or she loves, or as the voice of a friend or the sound of the telephone ringing.

Therefore, actual sounds do not exist outside our brains, even though there are physical vibrations we call sound waves. These sound waves are not transformed into sounds outside or inside our ears, but rather inside our brains. As the visual process is not performed by our eyes, neither do our ears perform the hearing process. For example, when you are having a chat with a friend, you observe the sight of your friend in your brain, and hear his or her voice in your brain. As the view in your brain is formed, you will have a deep feeling of three dimensions, and your friend's voice is also heard with a similar feeling of depth. For example, you could see your friend as being a long way from you, or sitting behind you; accordingly you feel his voice as if it is coming from him, from near you or from your back. However, your friend's voice is not far away or behind you. It is in your brain.

The extraordinariness about the real nature of the sound you hear is not limited to this. The brain is actually both lightproof and soundproof. Sound never in fact reaches the brain. Therefore, despite the volume of the sounds you hear, the interior of your brain is actually very quiet. However, you hear noise, such as voices, very clearly in your brain. They are so clear that a healthy person hears them without difficulties or distortions. You hear the symphony of an orchestra in your soundproof brain; you can hear all the sounds in a wide range of frequencies and decibel from the sounds of the leaves to the sounds of jet planes. When you go to a concert of your favorite singer, the deep and loud noise that fills the whole stadium is formed in the deep silence of your brain. When you sing by yourself loudly you hear the sound in your brain. However, if you were able to record the sound in your brain with a tape recorder at that moment, you would hear only silence. This is an extraordinary fact. The electrical signals that reach the brain are heard in your brain as sound, for example the sound of a concert in a stadium filled with people.

All Smells Occur In The Brain

If someone is asked how he senses the smells around him, he would probably say "with my nose". However, this answer is not the right one, even though some would instantly conclude that it was the truth. Gordon Shepherd, a professor of neurology from Yale University, explains why this is incorrect; "We think that we smell with our noses, [but] this is a little like saying that we hear with our ear lobes."9

A person smelling roses in his or her garden does not, in reality, smell the originals of the roses. What he or she senses is an interpretation of electrical signals by his or her brain. However, the smell seems so real that the person would never understand that he or she is not smelling the original rose, and some people therefore suppose that they are smelling the real rose. This is a great miracle created by God.

Our sense of smell works in a similar mechanism to our other sense organs. In fact, the only function of the nose is its ability to act as an intake channel for smell molecules. Volatile molecules such as vanilla, or the scent of a rose, come to receptors located on hairs in a part of the nose called the epithelium and interact with them. The result of the interaction of the smell molecules with the epithelium reaches the brain as an electric signal. These electric signals are then perceived as a scent by the brain. Thus, all smells which we interpret as good or bad are merely perceptions generated in the brain after the interaction with volatile molecules has been transduced into electric signals. The fragrance of perfume, of a flower, of a food which you like, of the sea-in short all smells you may or may not like-are perceived in the brain. However, the smell molecules never actually reach the brain. In our sense of smell, it is only electrical signals which reach the brain, as happens with sound and sight.

Consequently, a smell does not travel in any particular direction, because all smells are perceived by the smell center in the brain. For example, the smell of a cake does not come from the oven, in the same way that the smell of the dish does not come from the kitchen. Likewise, the smell of honeysuckle does not come from the garden and the smell of the sea, some distance away from you, does not come from the sea. All of these smells are sensed at one point, in a related area of the brain. There is no concept of right or left, front or back, outside of this sense center. Although each of the senses seem to occur with different effects, and may appear to be coming from different directions, they all in fact occur within the brain. The smells which occur in the smell
center of the brain are assumed to be the smells of outside materials. However, the image of the rose is generated in the sight center and the smell of a rose is generated in the smell center. If there is a genuine smell outside, you can never reach the original of it.

George Berkeley, a philosopher who has realized the importance of this truth, says "At the beginning, it was believed that colors, odors, etc., 'really exist,' but subsequently such views were renounced, and it was seen that they only exist in dependence on our sensations."

It may be instructive to consider dreams in order to understand that smell is only a sensation. When people dream, in the same way that all images are seen very realistically, smells are also perceived as if they were real. For example, a person who goes to a restaurant in his dream may choose his dinner amid the smells of the foods that are on the menu; someone who dreams of going on a trip to the sea side senses the distinctive smell of the sea, and someone who dreams of a daisy garden would experience, in his dream, the pleasure of the magnificent scents. Likewise, someone who dreams of going to a perfume shop and choosing a perfume would be able to distinguish between the smells of the perfumes, one by one. Everything in the dream is so realistic that when the person wakes up, he or she might be surprised by this situation.

In fact, it is not necessary to examine dreams to understand the subject. It is even sufficient to imagine one of the depictions that were mentioned, such as the example of the daisy. If you concentrate on the daisy, you can feel as if you are aware of its scent, even though it isn't there. The scent is now occurring in the brain. If you want to visualize your mother in your mind, you can see her in your mind, even though she isn't there in front of you; in the same way you can imagine the smell of the lily, even though it isn't there.

Michael Posner, a psychologist and Marcus Raichle, a neurologist from Washington University comment on the issue of how sight and other senses occur, even in the absence of an external stimulus:

Open your eyes, and a scene fills your view effortlessly; close your eyes and think of that scene, and you can summon an image of it, certainly not as vivid, solid, or complete as a scene you see with your eyes, but still one that captures the scene's essential characteristics. In both cases, an image of the scene is formed in the mind. The image formed from actual visual experiences is called a "percept" to distinguish it from an imagined image. The percept is formed as the result of light hitting the retina and sending signals that are further processed in the brain. But how are we able to create an image when no light is hitting the retina to send such signals?10

There is no need for an external source to form an image in your mind. This same situation holds true for the sense of smell. In the same way as you are aware of a smell which does not really exist in your dreams or imagination, you cannot be sure whether or not those objects, which you smell in real life, exist outside you. Even if you assume that these objects exist outside of you, you can never deal with the original objects.

All Tastes Occur In The Brain

The sense of taste can be explained in a manner similar to those of the other sense organs. Tasting is caused by little buds in the tongue and throat. The tongue can detect four different tastes, bitter, sour, sweet and salty. Taste buds, after a chain of processes, transform sensory
information into electrical signals and then transfer them to the brain. Subsequently, those signals are perceived by the brain as tastes. The taste that you experience when you eat a cake, yogurt, a lemon or a fruit is, in reality, a process that interprets electrical signals in the brain.

An image of a cake will be linked with the taste of the sugar, all of which occurs in the brain and everything sensed is related to the cake which you like so much. The taste that you are conscious of after you have eaten your cake, with a full appetite, is nothing other than an effect generated in your brain caused by electrical signals. You are only aware of what your brain interprets from the external stimuli. You can never reach the original object; for example you cannot see, smell or taste the actual chocolate itself. If the taste nerves in your brain were cut off, it would be impossible for the taste of anything you eat to reach your brain, and you would entirely lose your sense of taste. The fact that the tastes of which you are aware seem extraordinarily real should certainly not deceive you. This is the scientific explanation of the matter.

The Sense Of Touch Also Occurs In The Brain

The sense of touch is one of the factors which prevents people from being convinced of the aforementioned truth that the senses of sight, hearing and taste occur within the brain. For example, if you told someone that he sees a book within his brain, he would, if he didn't think carefully, reply "I can't be seeing the book in my brain-look, I'm touching it with my hand". Or, if we said "we cannot know whether the original of this book exists as a material object outside or not", again the same superficially minded person might answer "no, look, I'm holding it with my hand and I feel the hardness of it - that isn't a perception but an existence which has material reality".

However, there is a fact that such people cannot understand, or perhaps just ignore. The sense of touch also occurs in the brain as much as do all the other senses. That is to say, when you touch a material object, you sense whether it is hard, soft, wet, sticky or silky in the brain. The effects that come from your fingertips are transmitted to the brain as an electrical signal and these signals are perceived in the brain as the sense of touch. For instance, if you touch a rough surface, you can never know whether the surface is, in reality, indeed a rough surface, or how a rough surface actually feels. That is because you can never touch the original of a rough surface. The knowledge that you have about touching a surface is your brain's interpretation of certain stimuli.

A person chatting to a close friend while drinking a cup of tea immediately lets go of the cup when he burns his hand on the hot cup. However, in reality, that person feels the heat of the cup in his mind, not in his hand. The same person visualizes the image of the cup of tea in his mind, and senses the smell and taste of it in his mind. However, this man does not realize that the tea he enjoys is actually a sensation within his brain. He assumes that the glass exists outside of himself, and talks to his friend, whose image occurs again within his brain. In fact, this is an extraordinary case. The assumption that he is touching the original glass and drinking the original tea, which appears to be justified by his impression of the hardness and warmth of the cup and the taste and smell of the tea, shows the astonishing clarity and perfection of the senses which exist within one's brain.

This important truth, which needs careful consideration, is expressed by twentieth century philosopher Bertrand Russell:

As to the sense of touch when we press the table with our fingers, that is an electric disturbance on the electrons and protons of our fingertips, produced, according to modern physics, by the proximity of the electrons and protons in the table. If the same disturbance in our finger-tips arose in any other way, we should have the sensations, in spite of there being no table.11

The point that Russell makes here is extremely important. In fact, if our fingertips are given a stimulus in a different manner, we can sense entirely different feelings. However, as it will be explained in detail in due course, today this can be done by mechanical simulators. With the help of a special glove, a person can feel the sensation of stroking a cat, shaking hands with someone, washing his hands, or touching a hard material, even though none of these things may be present. In reality, of course, none of these sensations represent occurrences in the real world. This is further evidence that all the sensations felt by a human being are formed within the mind.

We Can Never Reach The Original Of The World That Occurs Within Our Brain

As has been demonstrated here, everything that we live through, see, hear and feel in our life occurs within the brain. For example, someone who looks out of the window while sitting on an armchair feels the hardness of the armchair and the slipperiness of the fabric in his brain. The smell of the coffee coming from the kitchen occurs in the mind, not in the kitchen some distance away. The view of the sea, birds and trees he sees from the window are all images formed in the brain. The friend who is serving the coffee, and the taste of the coffee also exist in the brain.

In short, someone sitting in his living room and looking out of the window is in reality looking at his living room, and the view seen from the window on a screen in his brain. What a human being would refer to as "my life" is a collection of all perceptions being put together in a meaningful way and watched from a screen in the brain, and one can never come out of one's brain.

We can never know the true nature of the original of the material world outside the brain. We cannot know, whether or not the original, for example the green of a leaf, is as we perceive it. Likewise, we can never find out if a dessert is really sweet or whether that is just how our brain perceives it to be. Imagine, for example, a landscape you have seen before. That landscape is not in front of you, but you are seeing it in your brain. The science writer Rita Carter says that we do not actually see the originals when see a face or a view, but an interpretation of the original or a version that is a complete reconstruction of it. She adds that no matter how well these copies are reproduced, they will still be different or inferior to the original. (Rita Carter, Mapping the Mind, University of California Press, London, 1999, p. 135)

The same thing applies to the time when you look at a landscape. There is in fact no difference between your imagining a landscape from a distance and seeing it close up. Therefore, when you look at a view you are actually seeing a version constructed in the brain, not the original.

Anyone who considers this will clearly see the truth. One such person, George Berkeley, expresses this truth in his work A Treatise Concerning the Principles of Human Knowledge:

By sight I have the ideas of light and colours, with their several degrees and variations. By touch I perceive hard and soft, heat and cold, motion and resistance... Smelling furnishes me with odours; the palate with tastes; and hearing conveys sounds... And as several of these are observed to accompany each other, they come to be marked by one name, and so to be reputed as one thing. Thus, for example, a certain colour, taste, smell, figure and consistence having been observed to go together, are accounted one distinct thing, signified by the name apple; other collections of ideas constitute a stone, a tree, a book, and the like sensible things...12

The truth Berkeley expresses in these words is this: We define an object by interpreting different sensations that are experienced in the brain. As is the case in this example, the taste and smell of an apple, its hardness and roundness and those sensations related with the other qualities of it are perceived as a whole by our brain and we perceive this whole as the apple. However, we can never actually deal with the original of the apple, only our perception of it. What we can see, smell, taste, touch or hear are only the copies within the brain.

When we consider all that has been discussed up to this point, the truth will be revealed in all clarity. For example:

If we can see a street full of colorful lights and all the colors with their own brilliant shadings inside the brain where there is no actual light, then we are seeing copies of the notice boards, lights, streetlights and the headlamps of cars which are produced from the electric signals within the brain.

Since no sound can enter the brain, we can never hear the original of the voices of loved ones. We hear only copies.

We cannot feel the cool of the sea, the warmth of the sun - we only feel the copies of them in our brains.

In the same way, nobody has been able to taste the original of mint. The taste someone would sense as mint is only a perception which occurs in the brain. This is because the person cannot touch the original of the mint, see the original of the mint or smell or taste the original of the mint.

In conclusion, throughout our lives we live with copy-perceptions which are shown to us. However, these copies are so realistic that we never realize that they are copies. For example, lift your head and have a look around the room. You see that you are in a room full of furniture. When you touch the arms of the armchair in which you are sitting, you feel the hardness of it as if you are really touching the original of it. The reality of these images shown to you, and the excellent artistry in the creation of these images are sufficient to convince you and billions of other people that the images are "material". Even though most people have read that every sensation relating to the world is formed in their brains, since it is taught in high school biology classes, the images are so convincing that they have difficulty believing that these images are only fantasies in their brain. The reason for this is that each image is created very realistically and perfected to an art.

Some people accept that images occur in the brain, yet they claim that the originals of the images are external. But they can never prove this, because nobody has been able to move out of the perceptions that exist in the brain. Everybody lives in the cell that is in the brain, and no one can experience anything except that which is shown by his perceptions. Consequently, one can never know what happens outside of his perceptions. Thus to say "there are originals outside" would in fact be an unjustified presupposition, because there is nothing that could be held up as evidence. Furthermore, even if there are originals outside, these "originals" will again be seen in the brain, meaning that the observer would deal with the images formed in his or her brain. Consequently such claims are unsupportable because people are unable to reach the "material equivalents" which they suppose to exist.

We should also emphasize that scientific or technological development cannot change anything, as every scientific discovery or technological invention occurs in the minds of people, and consequently is of no help to people in reaching the outside world.

The views of renowned philosophers like B. Russell and L. Wittgenstein on this subject are as follows:

For instance, whether a lemon truly exists or not and how it came to exist cannot be questioned or investigated. A lemon consists merely of a taste sensed by the tongue, an odour sensed by the nose, a colour and shape sensed by the eye; and only these features of it can be subject to examination and assessment. Science can never know the physical world.13

Philosopher G. Berkeley clearly expressed that our perceptions exist only in our minds and that we would be mistaken in automatically assuming that they exist in the outside world:

We believe in the existence of objects just because we see and touch them, and they are reflected to us by our perceptions. However, our perceptions are only ideas in our mind. Thus, objects we captivate by perceptions are nothing but ideas, and these ideas are essentially in nowhere but our mind… Since all these exist only in the mind, then it means that we are beguiled by deceptions when we imagine the universe and things to have an existence outside the mind. So, none of the surrounding things have an existence out of our mind. 14

In addition, it is of no importance for people whether something which a person cannot reach, see or touch, exists or not, because regardless of whether or not there is a material world, a human being only watches the world of perceptions in his brain. A person can never come across the true original of a material. Furthermore it is enough for everyone to see the copy. For example, someone who wanders around a garden with colorful flowers is not seeing the original of the garden, but the copy of it in his brain. However, this copy of the garden is so realistic that everyone receives some pleasure from the garden, as if it were real when in fact it is imaginary. Billions of people, right up until the present day, have assumed that they have been seeing the original of everything. Consequently, there is no reason for people to be interested in the "outside".

The Sense Of Distance Is Also A Perception That Occurs In The Brain

Imagine a crowd on a street, with shops, buildings, cars, horns honking… When you look at this picture it appears to be real. That is why most people cannot understand that the picture they see is produced in their brain, and mistakenly suppose that all of it is real. The picture has been created so perfectly that it is impossible to understand that the image that they perceive as real is not the original of the outside world, but only a copied image which exists in the mind.

The elements which make a picture so convincing and impressive are distance, depth, color, shade and light. These materials are used with such perfection that they become a three-dimensional, colorful and vivid image inside the brain. When an infinite amount of detail is added to the picture a whole new world emerges that, without realization, we assume is real for all life, although we only interpret it in our mind.

Imagine now that you are driving a car. The steering wheel is at arms length from you and there is a set of traffic lights about 100 m (or 300 ft) in front of you. The car in front of you is about 10 m (30 ft) away, while there are mountains on the horizon, which, according to your estimation, would be many kilometers (miles) away in the distance. However, all of these estimations are wrong. Neither the car nor the mountains are as far away as you would assume. In fact, the entire picture, as on a movie reel, exists on a two dimensional frame, on only one surface within the brain. The images reflected to the eye are two-dimensional, like those on a TV screen. In such circumstances, how can a perception of depth and distance occur?

What is referred to as a sense of distance is a way of seeing three-dimensionally. The elements causing the effects of distance and depth in images are perspective, shade and motion. The form of perception called spatial perception by optical science is provided by highly complicated systems. This system can be explained simply in this way: The sight which reaches the eye is two dimensional. That is to say, it has measures of height and width. The senses of depth and distance result from the fact that two eyes see two different images at the same time. The image that reaches each of our eyes differs from the other in terms of the angle and light. The brain assembles these two different images to form our sense of depth and distance.

We can perform an experiment to understand this better. First, extend your right arm in front of you and hold up your index finger. Now focus on this finger while closing your left eye first and then your right eye. Because two different visions come to each eye, you will see the finger move slightly to one side. Now open both of your eyes and while continuing to focus on your right index finger, move your left index finger as close to your eye as you can. You will notice that the closest finger will have created two images. This is because now a different depth has formed in the closer finger from that in the farther finger. If you open and close your eyes one by one, you will see that the finger located nearer your eye will appear to move more than the finger which is further away. This is due to the increasing difference in the views appearing in each eye.

While a three dimensional film is being made, this technique is used; Images shot from two different angles are placed on the same screen. The audience wears special glasses which have a color filter and polarize the light. The filters in the glasses filter out one of the two views, and the brain transforms these into one single three-dimensional image.

In this picture, the line in the back appears twice the size of the line at the front. However, in reality both of the lines are the same size. As we can see from this example, the use of lines, perspective, the light and shadow cause people to observe the same objects differently. In fact, all of these objects are viewed in a single place, in the visual center of the brain. On the bottom right can be seen a three-dimensional image on a building's wall.

The perception of depth in a retina with two dimensions is very similar to the technique used by artists to give the observer a feeling of depth in a picture with two dimensions.There are certain factors resulting in the feeling of depth, such as the placement of objects on top of one another, the atmosphere perspective, changes in texture, linear perspective, the dimensions, the height and the movement. For example the change of texture is very important in perceiving depth. For example, the ground that we walk on in a farm full of flowers is actually a tissue. The tissues closer to us are more detailed while the tissues further from us seem pale and harder to discern. Therefore, it is easier to estimate the distance of objects located on a tissue. Besides this, effects of shadow and light also contribute to the perception of a three-dimensional view.

One of the elements which provide the feeling of depth is tissue differentiation. Tissues closer to us can be observed in detail while those further away appear less clearly. For example as we can observe from the picture on the side, a three dimensional tissue has been created on a paper with the feeling of depth, and which seems to be embossed due to the use of color, shadow and light. Even though all the dots are white in the picture to the left, they appear to be flashing in both black and white.

The reason we admire a picture made by a successful artist is the sense of depth and reality which are given to the picture, which is created by using the elements of shade and perspective.

Perspective results from the fact that distant objects appear smaller in proportion to those which are nearer, depending on the person who is looking at it. For example, when we look at a view, distant trees appear small, while those nearby appear large. Likewise, in a picture with a mountain in the background, the mountain is drawn smaller than the person in the foreground. In linear perspective, artists use parallel lines. For example, train tracks produce an effect of distance and depth by meeting with the horizon.

The method that painters use in their paintings is also valid for the image that occurs in the brain. Depth, light and shade are produced by the same method in two dimensional space in the brain. The greater the amount of detail in the picture, the more realistic it appears and the more it deceives our senses. We behave as if there was real depth and distance, as if there was a third dimension. However, all pictures are like a film square on a flat surface. The
visual cortex in the brain is extremely small. The distances, the images such as those of distant houses, stars in the sky, the moon, the sun, airplanes flying in the air, and birds - they are all crammed into this small space. That is to say, there is technically no distance
between a glass that you can hold by extending your hand and an airplane that, if you looked up, you would understand to be thousands of kilometers above; all of them are on the single surface, that is, in the sense center of the brain.

For example, a disappearing ship on the horizon is not actually miles away from you. The ship is in your
brain. The window sill that you are looking at, a poplar tree in front of the window, the road in front of your house, the sea and the ship on the sea are all in the sight center of the brain, on a two dimensional surface. Just like a painter can represent the feeling of distance on a two dimensional canvas by using the proportions of size, elements of color, shade and light and perspective, so can the sense of distance also occur in the brain. In conclusion, the fact that we sense objects to be far away or nearby should not fool us, as distance is a sensation like all the others.

CREATING A PICTURE WITH DEPTH ON A TWO DIMENSIONAL SURFACE There is a very realistic depth in all of these pictures. A three-dimensional view with depth can be formed on a two-dimensional canvas by making use of shade, perspective and light. This element of realism can be increased depending on the ability of the painter. The same can be said for our own sight perception as well, as the vision that reaches the retina in fact exists in two dimensions. However, the images reaching each of our eyes become a single image, so that our brain perceives a three-dimensional image with depth.

Are You In The Room, Or Is The Room Inside You?

One of the reasons that prevent people from understanding that the images seen are actually sensed in the brain, is that people see their body in the image. They come to this wrong conclusion that "since I am in this room, the room does not occur in my brain." Their mistake is to forget that their body is an image too. Just like everything we see around us is an image which exists in the brain, so does our body also exist as an image in the brain. For example, while sitting on an armchair, you can see the rest of your body below your neck. This image too is produced by the same perceptual system. When you put your hand on your leg, you sense a kinesthetic feeling in the brain. This means that you see your body in the brain, and you feel yourself touching your body in the brain.

If the body is an image in the brain, is the room inside of you or are you in the room? The obvious answer to this is "the room is inside of you". And you see the image of your body inside the room, which in turn is in the brain.

Let us explain this with an example. Let us suppose that you call a lift. When it comes, your neighbor, who lives upstairs from you, is in it. You get into the lift. In reality, are you in the lift or is it in you? The truth is: the lift with the images of the neighbor and your body all occurs in your brain.

In conclusion, we are not "inside" anything. Everything is inside us; everything occurs in the brain. The sun, the moon, stars or an airplane flying in the sky many miles away cannot change this truth. The sun and the moon, like the book that you hold are only images which occur in a very small sight center in the brain.

Since your body is an image seen in your brain, the question is this: are you inside the room that you are in, or is the room inside you? The answer is clear: Of course, the room is inside you, in the vision center of your brain.

The World Of Senses Can Occur Without Outside World's Existence

One factor which invalidates the claim that the world of senses that we see has a material equivalent is that we do not need an outside world for senses to occur in the brain. Many technological developments such as simulators and also dreams are the most important evidences of this truth.

Science writer, Rita Carter, states in her book, Mapping The Mind, that "there's no need for eyes to see" and describes at length an experiment carried out by scientists. In the experiment, blind patients were fitted with a device that transformed video pictures into vibrating pulses. A camera mounted next to the subjects' eyes spread the pulses over their backs so they had continuous sensory input from the visual world. The patients started to behave as if they could really see, after a while. For example, there was a zoom lens in one of the devices so as to move closer the image. When the zoom is operated without informing the patient beforehand, the patient had an urge to protect himself with two arms because the image on the subject's back expanded suddenly as though the world was looming in.15

In an experiment, blind people were made to see some visions by a device. Through the device, these blind people could see some very realistic visions not belonging to the outside world but produced artificially. They were under the impression that something was coming towards them, so they stepped back to protect themselves.

As it is seen from this experiment, we can form sensations even when they are not caused by material equivalents in the outside world. All stimuli can be created artificially.