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.