Organizing the Rules of Nature

The title of this paper, "Organizing the Rules of nature", brings forth the question: What are the rules of nature? Since nature, exclusive of man, does not state any rules, the rules must be something that man creates by his study of nature. You will probably agree that the rules of nature as we know them are the principles of the sciences. But what are the principles of a science? What do scientists mean by "principle"? In 1947 I began asking biologists: What are the principles of biology? What do you mean by principle? I got no complete or consistent answers. I began noting how the word "principle" was being used and I listed every statement that some biologist called a principle. Most of these statements were generalizations by simple enumeration, but in my list were other kinds of statements. After years of questioning and reading and after years of studying the history and philosophy of science, I arrived at a simple definition of "principle". With few exceptions, the principles of biology are the major postulates of biological theories. But what are theories? If you go to biology textbooks, you will find loose and unclear definitions. Gibbs and Lawson (1), who reviewed 13 college and 8 high school textbooks, found the term "theory" is a state of confusion. To one author a theory is a general statement, to another a theory is a conceptual scheme, to another a theory is knowledge correct and complete, and to another a theory is a hypothesis repeatedly verified. The verified hypothesis view is quite common. But what is a "hypothesis"? Is a hypothesis a guess about an unknown fact, or an untested deduction, or a set of assumptions, or a theory in the making, or the postulate of a theory, or a tentative explanation? Unfortunately it is all of these as the word is now being used. Therefore to define theory in terms of "hypothesis" is no help. It simply compounds the confusion. According to A Dictionary of Ecology, Evolution and Systematics (2) a theory is "a scientifically accepted general principle supported by a substantial body of evidence offered to provide an explanation of observed facts and as a basis for future discussion or investigation." This definition is as misleading as those found in introductory textbooks. Is "All organisms are composed of cells" the cell theory? Certainly not. But it is a general principle strongly supported by evidence. "Inherited traits are determined by genes." This is another principle that is not a theory. So what is a theory? A theory is a nearly geometric pattern of reasoning. Central to each theory are a few ideas stated in the postulates (basic premises, fundamental assumptions). Lines of reasoning build pattern in three ways. 1) They use facts to support a postulate. 2) They use facts and postulates to explain known facts. 3) And they use facts and postulates to predict possible new facts. Theories with this structure are found everywhere in the natural and social sciences and in a few places in the arts and humanities. A theory is an intellectual construct consisting of a few basic premises plus many facts and lines of reasoning. A theory is a hypothetico-deductive system of thinking. The postulates are the hypothetico part of the system. Explanation and prediction are the deductive parts of the system. Figure 1 is a diagram of a theory. The P’s at the top are the postulates, the basic premises, of the theory. Usually there are from 5 to 9 postulates. The arrows represent lines of reasoning. The F’s represent facts and Pr, predictions. R1 is a line of reasoning that uses facts to support one or another of the postulates. R2 is reasoning that uses the postulates and facts to explain a possible new fact and R3 is reasoning that uses postulates and facts to predict a possible new fact. This diagram is misleading because it looks as though the bulk of the theory is the basic premises, the postulates, whereas they are usually the smallest part of a theory. The great bulk of a theory consists of dozens, hundreds, or thousands of facts and lines of reasoning.