Law and Thomistic Exemplarism

LAW AND THOMISTIC EXEMPLARISM JOHN PETERSON University of Rhode Island Kingston, Rhode Island CIVIL LAW differs from empirical law in that the former prescribes regularities in human action while the latter describes and predicts regularities in the world apart from human action. By an empirical or descriptive law scientists mean a law that is knowable on the basis of observed regularities . An example is Boyle's law. That at a constant temperature the volumes occupied by a constant mass of gas are in inverse ratio to the pressures they support is an observed regularity. This law also describes and predicts a regular occurrence in the world apart from human action. The same is true of Galileo's law that the acceleration of free fall on Earth is thirty-two feet per second per second. But the law that citizens ought to pay taxes in proportion to their incomes prescribes a type of action human beings are obliged to take at regular intervals. A notable difference is that predictability is much lower in the case of civil law than it is in the case of empirical law. You can infallibly predict that the inverse ratio of volumes to pressures in a gas will hold in the next case or that the next free fall will accelerate at thirtytwo feet per second per second. But that your neighbors will pay their fair share of taxes next year is a risky guess. This is part of what it means to say that empirical natural laws are in the world in a way that the laws of society and the state are not. Events, activities, or relationships in the world do not fail to conform to laws whereas actions of citizens often fail to conform to the laws of the state. From empirical laws scientists distinguish theoretical laws. These more general laws are usually called theories or hypotheses . Unlike empirical laws, theories are never generalizations drawn from observations of phenomena. Moreover, theories are often the explanation of empirical laws. So the latter both enter 81 82 JOHN PETERSON into the explanation of a phenomenon and are for their own part explained by theories. Empirical laws are thus both explanans and explanandum as regards phenomena and theories respectively . Thus, Galileo's law of acceleration both enters into the explanation of the particular event of the free fall of this stone at thirty-two feet per second per second and is itself partly explain~d by Newton's laws of motion and his law of gravity.1 But whether or not causal-deductive explanation includes empirical laws that are themselves explained by theoretical laws, all such explanation includes both explanandum and explanans. The former is always some empirical phenomenon. And the latter , as Carl Hempel and Paul Oppenheim point out, is generally made up of two parts, a law or laws and statements of fact or antecedent conditions.2 In the following schema the first two lines comprise the explanans and the last line the explanandum. Thus: C1, C2, ... , Cn (statements of conditions) L1, L2, ... Ln (laws) E (description of phenomenon to be explained)3 While much causal-deductive explanation in science follows this pattern, not all of it does. For while the explanans must include a law, it need not include a statement that is not a law. For example, Hempel and Oppenheim cite the case in which the regularities that govern the motion of the double stars are explained solely in terms of the laws of celestial mechanics.4 In any case, whether it is the explanandum of a theory or the explanans of a particular observed phenomenon, an empirical law has these three characteristics: first, it is originally based on observations; second, no term in the statement of it fails to occur in the observation statements from which (in the order of knowl1 Carl G. Hempel and Paul Oppenheim, "Studies in the Logic of Explanation," in Janet A. Kourany, ed., Scientific Knowledge: Basic Issues in the Philosophy ofScience (Belmont, Cal.: Wadsworth, 1987), 31. 2 Ibid., 31.·1 Ibid., 32. 4 Ibid., 31. LAW AND THOMISTIC EXEMPLARISM 83 edge) it is based; and third, no values of its variable terms are determined in relation...