Many people have talked about the nature of mental images. Concerning mental images, for example, I have one of the Franklin mountains around which the city of El Paso is laid out. Theyre not big mountains, such as those in Alaska. The highest peak rises only about 1,000m. They are, however, a dominant feature of the horizon line to the north of my fathers house, etching a midline gray stone and yellow green break across the sightline.

The front steps of the house face west approximately. When you leave the house and begin down the five concrete steps you note the sun and the forehead of the mountain to the left of it, at about northwest. Its fair to say that its the first thing you see in the morning. Its an imposing image, an image you watch and watch long, even though the features of the mountain, stone ridging, bandings of sandstone, and just the suggestion of yucca, Spanish Dagger, and desert grass and desert wild flowers, become familiar. The surface changes with the position of the sun. Dark blue and purple in the morning at dawn; then phases of common daylight which dulls the surface, then orange, pink, purple at dusk. Given the cloud cover or the amount of pollution and dust in the air in the evening, all the hues find their way across the creases and folds of mountain. Storms often move in from the southwest, their moisture drawn up from the Gulf of Mexico, thus in evening, the sun will burn sherbet orange on the mountain slopes in its lower course, while the deep gray and blue and black of desert storms wall off the western world.

Above it all you can see the bloated white crowns of the clouds, rising and splitting in the high atmosphere. For the kids, such a sight was familiar and suspenseful and scary, watching a thunderstorm as a total vertical and horizontal phenomenon, for the adults, nostalgic.

Other images of the mind, or in the mind, are more spread out, diffused, or hard to fix, instances of time that we remember, recall, such as sitting on the porch in the cool and sunny air of a spring morning in Connecticut. The image of the mountain is an object. It has physical density. Its image, which no science has been able to explain mechanically, translating the surfacing of certain kinds of memory from electrical signals and stimuli (this is similar to asking what is the nature of consciousness), matches the real object pretty well as light in the mind. The mountain has a ready quality of recognition even as two distinct phenomena. The mountain has objective quantity but the mental image of the mountain, which isnt the mountain, is difficult to describe with conventional descriptive language as an occurrence. The physical mountain takes up space, but what sort of space does the mental image of the mountain take up in my mind? I know that the image takes up time, thus, to accord Einstein his due, it must have some spatial quality. Is the memory or image of the mountain quantifiable in spatial termshaving mass, position, energy, some physics beyond the mechanism of brain–or is it more like an effect of physical fields which the brain translates, such as gravitation or electromagnetism?

Regardless, the power of the image remains, the power of the shadow of what made it lurking just a few seconds away in thought, always.