Attention:

Aldous Huxley in his famous book, The Doors of Perception saw the brain as a limiting valve. The idea of the brain as organ of perception is either erroneous or only partly true. The brain shuts out unwanted stimuli rather than perceiving and responding to them. Huxley wrote in thrall of a mescaline experience whose effect was to enhance perception, seeing “The all in every this.,” as he put it. The ordinary individual under the influence, can see things like an artist, Istigheit or is-ness of objects, in and of themselves, freed of the ego of the observer. Huxley was struck by Vermeer’s complex task of drawing or sculpting fabric , as Isaacson did of Leonardo. How long DaVinci worked to master the shadows and light in the particular way a curtain falls! For the artist and hallucinating explorer, the mundane turns astounding. The individual thing becomes universal, much like the religious person saying a blessing over every little thing, thanking the one above for waking up, for a morsel of food, for being able to go to the bathroom. The blessing sanctifies common things making everything holy. The particular is elevates to the universal.
Suppose each detail is so magnificent of itself, then your brain could not possibly process fully what’s around you. You couldn’t get anything done. The brain has no choice, according to that point of view, but to focus, and filter practically everything out. The task of one’s brain is never to perceive fully but to exclude the full magnificence of the world.
That explains why looking at photos and videos of my travels always sets me wondering. “Wow! Did I really see and hear all that, did I have that great a time?” I don’t remember seeing intense color, having that much fun. But yes it must be true. Lenses and microphones don’t lie. The brain, doesn’t help you see, Huxley says, but inhibits or occludes. The brain is editor of full experience. It is an attractive proposition that the brain limits seeing true splendor, and that certain drugs or religious experiences allow a faint glimpse into the world of wonder, casting the eyes heavenward. The brain is a sun filter or polarizer, protector. Should your pupils fail to constrict you’ll be blown away by the light.
Yet that is a partial view. The purpose of attention is direction of perception and action. From the sober neurological perspective, attention is purpose driven, directing the organism to efficient accomplishment of a task which will necessarily exclude irrelevant elements. Your brain helps you to survive the cruel world, no better or worse than liver or kidney.
Arguments to the contrary are to come.
“If the doors of perception were cleansed every thing would appear to man as it is, Infinite. For man has closed himself up, till he sees all things thro’ narrow chinks of his cavern” – Famous quote of Wm Blake The Marriage of Heaven and Hell, 1790
See also Plato’s allegory of the Cave.