Our senses and our world, part three

If we agree that a tomato in the dark refrigerator is only potentially red—not truly red when no light is shining on it—then must we agree that the properties of objects do not exist when they are not perceived? Is sugar not sweet when it is not being tasted? And is salt not salty when it is not being tasted? Are they only potentially sweet and potentially salty? If that is the case, then we have abandoned dualism and are functioning in the realm of idealism. In that realm, minds and thoughts and ideas (and spirits) are real, but the material world is only in illusion formed by our minds and thoughts and ideas (and spirits).

Imagine a small pile, half a teaspoon, of white crystals on the kitchen counter. They might be sugar or salt, but you don’t know which. Clearly, by tasting a few of the crystals, you will know if the pile is sugar or salt. Does that mean that the crystals are neither sugar nor salt until they have been sampled?

Taste is the quickest way to discern sugar from salt, but a chemist could provide other tests that would identify the crystals apart from their taste. Sugar consists of hydrocarbon molecules, but table salt is a lattice of sodium and chlorine ions. These chemical facts remain true even if the crystals are not tasted. Therefore, we do not have to taste them for them to be either sweet or salty.

By the same token, the brown table in the center of the room is not brown in the dark, but it is still a table, hard and unyielding. If I walk into that table in the dark, it will bruise my shin and cause me to lose my balance. Even in the dark, when it is no longer brown, that table retains all its other physical properties as a material object.

If a tree falls in the forest and no one is there to hear it, does it make a sound? As it begins to tumble, it crashes into other trees, and the crackling of the branches sends vibrations through the air. When it finally hits the ground, it creates a thump that shakes the ground. That thump will be discernable for some distance in the ground, and it also will cause vibrations in the air. Now perhaps no person is in the forest to hear the crackling and the thump. If a scientist has left a listening/recording device in the forest—trying to gather evidence of a surviving ivory-billed woodpecker or of Bigfoot—that device will register the sound of the falling tree. Squirrels and sparrows will hear the crackle and the thump. But what if there are no squirrels, no sparrows, and no scientific listening device? Will the tree still make a sound? A Christian (or Muslim or Jew) is likely to say that God is still in the forest. God will hear the sound of the falling tree. If God is not present, then there is no tree and no forest, and (of course) no sound. On the one hand, this proposal lends itself to Berkeley’s brand of idealism—things we call material are ideas in the mind of God, and as a result they are real to all created beings that have senses and minds.

But a tree is big enough to make a sound. One leaf, falling from the tree, might not make a sound that is heard by any human being, squirrel, sparrow, or scientific device. Does God still hear the leaf when it lands on the floor of the forest? Perhaps. Philosophy alone cannot answer that question.

But substances in the material world must have a certain quantity to possess the qualities we apply to those substances. The half-teaspoon of sugar or salt was sweet or salty. One molecule of sugar, or one sodium ion linked to one chlorine ion, would have no flavor. Half a teaspoon of water is wet. One molecule of water is not wet. A steel knife is sharp. One iron molecule from that knife is not sharp.

I will address the atomic theory of material substances more completely a bit later in this writing. But we must concede right now that the smallest particles of matter lack the qualities that they attain when they gather in large numbers. A single molecule of chlorophyl is not green. It is too small to reflect any light. But millions of molecules of chlorophyl, gathered in the same leaf, are green. This fact forces us to reconsider our opinion about the reality of the material world, that world which is revealed to us by our senses. J.

Our senses and our world, part one

We experience the world around us through our senses. Traditionally, we are attributed with five senses: sight, hearing, touch, taste, and smell. Taste and smell are similar enough in nature that they often are lumped together as one sense. At the same time, modern physiologists speak of other senses which we possess, such as the sense of balance. These additional senses tell us about our own body rather than about the outside world, so we can set those aside as we explore philosophy.

Still other people mention additional senses or sense-like perceptions. They suggest that we gather information about the world in ways that transcend the usual five senses. They speak of a sixth sense or of Extra-Sensory Perception (ESP). unfortunately, scientific investigation into those additional senses usually reveals either fraud or mere coincidence. Much of what we attribute to a sixth sense comes more from information acquired through the five senses and from rational (if often less than conscious) consideration of that information gathered in the present or remembered from the past.

So we are left with sight, hearing, touch, and taste-and-smell. Each of those involves input from the world beyond our bodies. Sight involves light, perceived by our eyes and reported to our brains. Hearing involves sound, perceived by our ears and reported to our brains. Touch involves contact with our skin, perceived by nerve-endings in our skin and reported to our brains. Taste and smell involve small particles that reach receptors in our mouths and noses that report to our brains what they perceive. In all these cases, our brains receive this information, evaluate its importance, and generate a response—ranging from ignoring the information to enjoying the experience, remembering the source of the stimulus so it can be repeated or avoided, or even rushing to flee from the cause of the stimulus.

Over the centuries, philosophers meditated on sight and discussed its significance. They pondered whether a color—white, for example, or red—was an essential part of an object or merely a characteristic of an object. They asked whether a color, such as white or red, can exist apart from an object. (Is the idea of whiteness real, or is it merely a label applied to all objects that have the characteristic of being white?) They debated how colors are perceived by our minds, and they asked whether we all see the same thing when we look at an object.

Modern scientists tell us that light comes in various wavelengths. Whiteness is a combination of wavelengths, which scientists demonstrate by shining white light through a prism, which breaks the light into the colors of the rainbow. Red and orange and other colors are distinct wavelengths of light. We see light emitted by some objects—the sun, of course, and flames, and wires or bulbs of light that glow due to electric current. Other objects reflect light. If the source of the light is red, the objects that reflect that red light will all look red. But white light shining on objects will have some wavelengths absorbed by the object and others reflected. As a consequence, when white light shines, we will see red objects and green objects and blue objects and many other colors as well.

Certain trees and other broad-leafed plants change color. In the spring and summer, they have green leaves. That green is caused by chlorophyl, which absorbs other wavelengths of light but reflects green light. In autumn, plants stop producing chlorophyl, and other chemicals in the leaves reflect other wavelengths of light—red, orange, yellow, or brown. Those leaves then fall off the plants and die, and in the spring new leaves are produced to replace them. We see different colors of leaves at different times of the year because of different chemicals in the leaves which reflect different wavelengths of light.

Arguably, an object in the dark has no color, because it is reflecting no light. An apple or tomato in the drawer of a closed refrigerator has the potential to be red, but it is not red when it is in the dark. (Yes, I know that apples and tomatoes last longer when they are not refrigerated, but the example is still valid.) Open the door of the refrigerator, let light shine on the apple or tomato, and they are red. They do not lose their ability to be red by being in the dark. But potential color is real color only when light is reflected by an object.

We see more than color. We also see shapes and sizes and other qualities of the objects within our view. Our brains are adept at interpreting what we see, even when what we see is a distortion of what is really there. This fact has caused some philosophers to wrestle almost endlessly with the relationship between sight and reality. For example, in the center of my reading room is a square table. Only by standing directly over it and looking down at it do I really see a square. From my favorite chair, or from the doorway, the table would not seem to be square. A photograph or painting from either perspective would contain a tabletop with four sides, but those four sides would not form a square. Yet not only do I recognize that the table is square from every other perspective; a visitor to my house, looking from the doorway into the reading room, would recognize that the table is square. Partly because we have two eyes (which provides some perception of depth) but more because our brains are effective at interpreting what our eyes report, we see the true shape of objects even when our perspective should distort the shape of those objects.

In the same way, I know that the person standing next to me is much shorter than a distant tree, even though the tree occupies much less of my field of vision than the nearer person. Our brains have awareness of depth perception and of the fact that distant objects are bigger than they appear. Therefore, our brains are fooled only when we cannot know either the size or distance of an object. Ancient philosophers and scientists thought that the sun was both smaller and nearer than it really is, because at the time they had no way of measuring its true size or its true distance. In most cases, though, people are able to estimate the size of seen objects accurately because of knowledge and experience of the world and of the way it works.

Yet our eyes can be fooled. A spoon in a glass of water appears to be bent because of the difference between the way light flows through water and through air. Distracted and preoccupied, our minds sometimes miss sights that our eyes have recorded or wrongly interpret what they eyes report. And, naturally, we cannot see things when something else is in the way—we cannot see the apple in the refrigerator when the refrigerator door is closed. Our experience of the world, as gained through sight, remains limited.

And we do not always see what other people see. In 2015, a woman photographed a dress in a store and sent the digital photograph to her daughter. The dress was blue and black, but when the daughter saw the photograph, she thought she was looking at a photograph of a white and gold dress. Over the following months, millions of people saw the same photograph. Even looking at the same photograph on the same device at the same time, some saw a blue and black dress, while others saw a white and gold dress. Our minds process information received from the eyes in a variety of ways, drawing clues about color and shape and size from many past experiences and impressions. Living in the same world, we do not always experience the same thing. Reality does not change from person to person—the real dress was blue and black. But perception and interpretation can lead to differences, sometimes such significant differences that we appear to be living in different worlds. J.