The Impact of Rigid Definitions on Scientific Thinking

THE IMPACT OF RIGID DEFINITIONS ON SCIENTIFIC THINKING D. B. ZILVERSMIT* I. Language and the External World Bertrand Russell [i] has said that language suggests a definiteness, discreteness , and quasi-permanence ofobjects which physics seems to show do not exist. Ifthis is true oflanguage in general, it is even more true of definitions. And ifthis rigidity bothers us in everyday communication, it constitutes an even more serious threat to our ability to think in scientific terms about the universe. Linguistic problems were not recognized by the ancient philosophers. Theyassumedthatlanguage, theirlanguage, provided aperfect instrument for describing the external world. To a large extent it did, ofcourse; ifit had not, so many oftheir thoughts would not have survived. Although the beginnings oflanguage cannot be traced with certainty, we imagine that it stemmed from the desire to fulfil primitive needs. Calls for food, cries ofwarning, and melodious utterances associated with courting a potential mate probably developed into a more intricate language pattern, which required, however, a more or less steady relation between the external situation and the sound used to designate the situation. Soonprimitive man must have discovered that a separate word for each object or event led to an impossibly large vocabulary. Let us imagine a conversation between a primitive young man and his equally primitive girlfriend—and as long as we are imagining in English, we will cast their remarks in that language. The boy wishes to give his beloved some permanent token ofrecognition between them and selects a nice young tree with budding leaves. The girl, in ecstasy, signifies her pleasure by calling the fresh green color "verdant." At their next meeting * University of Tennessee, Department of Physiology, Memphis 3, Tennessee. Career Investigator ofthe American Heart Association. 227 under the tree "verdant" is repeated many times and is now firmly established , not only for what we would call green, but for "this fresh springlike -appearing green." As the days go by and other meetings take place, both boy and girl notice that their verdant tree is changing; it takes on a darker shade. They may continue to use the word "verdant" to describe the new situation but imply now that it stands for darker shades ofgreen associated with plants as well as for "fresh green." The process ofabstraction has begun. As the year continues, the color ofthe leaves changes even more. Perhaps we would now call the leaf red or brown. Our young couple, however, may not yet have any need for a new word. So long as the designation "verdant" does not create a conflicting situation, they would probably continue to use this word. With our more sophisticated language, we would describe this mechanism of word development by saying that "verdant" gradually assumes a more abstract meaning, perhaps something more akin to our word "colored." The couple will continue to use their new word to describe all the experiences that seem to have some spatial or temporal continuity with the original situation. Only after new situations arise in which "verdant" is ambiguous or creates some erroneous mental picture is a new word needed. Then perhaps "green" and "red" are coined, and "colored" includes all of them. Before long, definitions are required to transmit to others the differences between these words. This is the topic which I will discuss more in detail. What do we mean by a definition? This question is much too broad for a comprehensive answer. In his book entitled Definition, Robinson [2] distinguishes several categories. It would take us too far afield to discuss them in detail, but for the sake ofperspective I will mention the relevant aspects. Definitions can be divided into real and nominal définitions. A real definition characterizes a "thing" or an "event." It seeks to establish the essence ofsomething. A classical example, from Plato, is Socrates and his students trying to establish the essence ofvirtue andjustice. A more contemporary example might be a statement concerning the nature ofthe electron or an answer to the question, "What is the nerve impulse?" In science a real definition is the end result ofa scientific investigation. A physiology textbook does not usually begin with a statement of what physiology is and then proceed to test...