The Generality of Hypothetico-Deductive Reasoning: Making Scientific Thinking Explicit

L EWIS (1988) made the case that today's biology is essentially hypothetico-deductive in nature. In Lewis's view, biology is not a in which one gathers all the facts, classifies them and then somehow crystallizes them into theory. In Lewis's words, This erroneous view of method plus the absence of a proper definition of theory misguided my early development in science (p. 362). The failure of Lewis's teachers and textbook authors to portray as a hypothetico-deductive enterprise not only misguided his early development as a scientist, but some teachers and textbook authors continue to misguide today's students as well. Therefore, in an effort to better understand the extent to which not only biology, but also geology, physics and chemistry are hypothetico-deductive in nature, examples of the use of hypothetico-deductive thinking in these disciplines have been sought, as have examples of use of the method in solution of practical human problems. The purpose of this paper is to present these examples so that teachers can use them to explicate how biology, as well as other sciences, is largely hypothetico-deductive in nature. Indeed, the examples will show that hypothetico-deductive thinking is not at all new to as it can be found in research from the Middle Ages. A key element in making hypothetico-deductive thinking explicit to students is to cast it in the form of If ... and ... then ... And/But ... Therefore ... arguments. Making thinking explicit in this way is helpful because scientists seldom make their hypothetico-deductive reasoning explicit. In fact, their writing often obfuscates thinking. Further, as pointed out by Gibbs and Lawson (1992), most biology textbook writers do little better, if at all, at explicating the use of hypotheticodeductive reasoning. Let us start with early theories of blood flow and the classic research of William Harvey to see how his thinking can be cast in the form of hypothetico-deductive arguments. Early Theories of Blood Flow & William Harvey's Research