Karl Popper, Verifiability, and Systematic Zoology

Abstract

Kitts, D. B. (Department of the History of Science, and School of Geology and Geophysics, University of Oklahoma, Norman, Oklahoma 73019) 1977. Karl Popper, verifiability, and systematic zoology. Syst. Zool. 26:185-194.-Karl Popper maintains that the laws of science are not, in principle, verifiable but only falsifiable because they are formulated in strictly universal statements which refer to an unlimited number of instances. Several taxonomists have apparently concluded that the knowledge of systematic zoology is expressed in these strictly universal statements. It is argued in this paper that the knowledge claims of systematic zoology are formulated in what Popper has called numerically universal statements which are equivalent to conjunctions of a finite number of singular statements and that they are, therefore, in principle, both verifiable and falsifiable. [Systematic zoology; Karl Popper; universal statements; verifiability; falsifiability.] During the past decade a number of authors (see for example: Bock, 1973; Gaffney, 1975; and Wiley, 1975) have attempted to apply Karl Popper's philosophy of science (see especially, Popper, 1959) to systematic zoology and paleontology. In this paper I shall claim that these authors have misunderstood one of Popper's principal claims about the nature of science and that they are also mistaken about the meaning of the statements in which systematic zoological knowledge is expressed. In Popper's view the theories, or natural laws, of science are to be regarded as strictly universal statements. A strictly universal statement, according to Popper, claims to be true for any time and any place and for an unlimited number of individual cases. of this kind are to be contrasted with numerically universal statements which refer to a finite class of elements within a particular spatiotemporal region. Natural laws formulated in strictly universal statements cannot be verified because in Popper's words (1959:63), For the verification of a natural law could only be carried out by empirically ascertaining every single event to which the law might apply, and by finding that every such event actually conforms to the law-clearly an impossible task. Events which conform to a law can never justify its strictly universal claim but just one event which does not conform to the law can falsify its universal claim. It is thus that scientific laws are in principle falsifiable but not verifiable. Popper emphasizes that the process by which laws are tested is deductive. Scientific laws, being strictly universal, do not refer to particular times and places, and therefore do not immediately provide us with events whereby they might be tested. about events which can be empirically tested must somehow be generated. This is accomplished by deducing singular statements describing particular events from the strictly universal statements of the theory together with singular statements describing initial and boundary conditions. If the singular descriptive statement deduced from the theoiy is consistent with the theory then it provides a reason not to abandon it but clearly does not verify it. If the singular descriptive statement deduced from the theory contradicts it then the theory is falsified. It is important to note here that it is only strictly universal statements that can be in principle falsified but not verified. Numerically universal statements, though logically indistinguishable from strictly universal statements, differ from them in an important way. Popper says of numerically universal statements (1959:62): Statements of this latter kind can, in prin-