Perception and Reality

Let us take vision as an example. When I look at a tree, light reflected from its leaves is focused onto the retina of my eye, where it creates an image of the world "out there". Photo-sensitive cells in the retina absorb the light's energy, triggering a series of chemical reactions that release electrons. Neurons connected to the cells amplify these discharges and turn them into electrical impulses which are carried by the optic nerve back to the brain. Here the raw data undergoes a complex array of processes that extract from it shapes, patterns, colors, movements and other features. Comparing these with past experiences, expectations, and other information, the information is integrated into a single picture, and and an image of the tree appears in my consciousness. Just how this happens is the "hard question" we touched on earlier, and we need not trouble ourselves with it anymore for the moment; but what is undeniable is that it does happen. There arises the conscious experience of seeing the tree.

Similar processes happen with the other senses. Vibrations in the air emanating from a violin trigger minute hairs in the ear, sending electrical impulses to the brain where they undergo an equally complex and unfathomable processing, which culminates in the experience of a sound. Pressure sensitive cells in the skin relay messages back to the brain, that give rise to the experiences of touch, texture and movement. Receptors in the nose and tongue, sensitive to certain molecular structures likewise send data to the brain where, in the same mysterious manner, they give rise to experiences of smell and taste.