Natural Law Theories
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Philosophy Compass 11/2 (2016): 91–101, 10.1111/phc3.12315 Natural Law Theories Jonathan Crowe* University of Queensland Abstract This article considers natural law perspectives on the nature of law. Natural law theories are united by what Mark Murphy calls the natural law thesis: law is necessarily a rational standard for conduct. The natural law position comes in strong and weak versions: the strong view holds that a rational defect in a norm renders it legally invalid, while the weak view holds that a rational defect in a legal norm renders it legally defective. The article explores the motivations for the natural law position, before considering three lines of natural law argument found in the literature. I conclude by examining the arguments offered by John Finnis and Murphy in support of the weak natural law view. I suggest that these arguments fail to impugn the strong natural law thesis. Indeed, the functional argument outlined by Murphy provides a plausible route to a hybrid natural law view that incorporates both weak and strong claims. A theory of law, according to Joseph Raz, aims to identify necessary truths about law that explain what it is (2005, 324). What sorts of claims about law plausibly fall into this category? Here are two possible candidates: (1) Law is necessarily a socially recognised standard for conduct. (2) Law is necessarily a rational standard for conduct. Claim (1) is almost universally accepted among contemporary legal philosophers. However, (2) is disputed. Mark Murphy calls (2) the natural law thesis (2003, 244; 2005, 15); views that endorse it are known as natural law theories.1 The basic thought behind (1) runs as follows. Social conventions designate particular people, bodies and practices as holding the capacity to create or modify legal norms. Legislatures, for example, are recognised as having the authority to create new laws, while judges are recognised as having the power to make legally binding decisions. Legal officials seek to apply these conventions when identifying legal constraints on their actions. A norm holds legal status only if it is recognised by these sources. The existence and content of law is therefore a matter of social fact. This basic picture, as I said, is generally accepted. However, views differ on whether it tells the whole story. One such dispute concerns rational constraints on lawmaking. The basic thought behind (2) concerns the role laws play in the community. The function of law, it seems, is to guide action. It exists to mark the boundaries of permissible social conduct. Law that fails to supply adequate reason to do as it requires is poorly adapted to this role. This suggests that law’s capacity to play its function depends on its ability to engage human reason. Furthermore, law typically claims to guide action in the service of some higher goal, such as justice or the common good. A standard that runs contrary to justice or the common good therefore seems defective as law. 1. Strong and Weak Natural Law The leading contemporary legal philosophers working within the natural law tradition – includ- ing John Finnis (2011a), Murphy (2006a, 2013), Michael S. Moore (1992, 2001), Robert Alexy © 2016 The Author(s) Philosophy Compass © 2016 John Wiley & Sons Ltd 92 Natural Law Theories (2008, 2010a, 2010b), Lon Fuller (1969) and Michael Detmold (1984) – all endorse some varia- tion on (2). However, the claim comes in strong and weak versions (Murphy 2006a, ch. 1; Murphy 2013; Crowe 2012, 164–6).2 The natural law thesis holds that law is necessarily a rational standard for conduct. What, then, should we say about a putative law that fails this standard? The strong natural law view interprets the natural law thesis as stating an existence condition for law. Law is a rational standard for conduct in the same way that a square is a shape with four sides: anything that fails this standard fails to qualify as law. The weak natural law view, by contrast, interprets the claim as stating a non-defectiveness condition for law. Law, on this view, is a rational standard for conduct in the same way that an alarm clock is a device that wakes people up in the morning: anything that fails this standard either fails to count as law or is defective as law. The strong view, then, holds that a rational defect in a norm necessarily renders it legally invalid, while the weak view holds that a rational defect in a legal norm necessarily renders it legally defective. The two leading contemporary natural law theorists, Finnis and Murphy, both favour the weak view, albeit for different reasons. (I will consider their views more closely later in this article.) The leading contemporary defender of the strong view is Moore (1992, 2001), but versions of the claim are also defended by Fuller (1969, 39) and Alexy (2008, 281; 2010, 177).3 2. Natural Law and Legal Positivism An opposition is traditionally drawn between natural law theories and legal positivism. We have seen that natural law theories emphasise that law is a rational standard for conduct. The legal positivist tradition, by contrast, focuses on the idea of law as a socially recognised standard. Legal positivist views, like natural law theories, come in two main varieties. Inclusive legal positivism holds that social sources are the only necessary factor in determining legal status (see, e.g. Hart 2012, 250–4; Coleman 2001, 67–148; Waluchow 1994). In some legal systems, however, the recognised social sources may incorporate rational standards into the test for legal validity. A commonly cited example is the Eighth Amendment to the United States Constitution, which prohibits ‘cruel and unusual punishments’. One view of this provision is that it makes the validity of laws relating to punishment dependent on their reasonableness. Inclusive legal positivism therefore accepts that, in some legal systems, whether some- thing is a law may depend on not only its sources but also the rationality of its content. This, however, is a contingent matter depending on social practices. Exclusive legal positivism, on the other hand, holds that the existence and content of law can only ever depend upon social facts (see, e.g. Raz 1979, ch. 3; Raz 1995, ch. 10; Shapiro 2001). It is therefore necessarily true that whether something counts as law does not depend on its rationality. A provision like the Eighth Amendment, on this view, does not incorporate rational standards into the law. Rather, it gives judges a discretion to create new legal norms about the meaning of ‘cruel and unusual punishments’. The content of law there- fore still depends on its sources, not its merits. Inclusive and exclusive legal positivism are united by the claim that social sources are the only necessary factor in conferring legal status. Exclusive legal positivism also makes a more robust claim: necessarily, whether something holds legal status only depends on social sources. This yields the following two views: LPI The only necessary factor in determining whether something counts as law is recognition by social sources. © 2016 The Author(s) Philosophy Compass 11/2 (2016): 91–101, 10.1111/phc3.12315 Philosophy Compass © 2016 John Wiley & Sons Ltd Natural Law Theories 93 LPE It is necessarily true that whether something counts as law depends only on recognition by social sources. Both versions of legal positivism contradict the strong natural law view that a rational defect in a norm necessarily renders it legally invalid. However, they are technically compatible with the weak natural law view that a rational defect in a norm renders it legally defective. Both LPI and LPE concern the existence conditions of law; they have nothing to say about when a legal standard is defective. The potential for convergence between weak natural law theories and legal positivism is apparent in the work of authors from both traditions. Finnis, for example, effectively affirms LPI as an account of the existence conditions of law (2011a, ch. 10; 2011c, 185), while Neil MacCormick has endorsed the weak natural law claim within a legal positivist framework (1992, 108). There are, however, significant methodological differences between the natural law and legal positivist outlooks (cf. Murphy 2006a, 23–4). Natural law theories, by focusing on the idea that law is a rational standard for conduct, tend to take the view that one cannot have a complete descriptive theory of law without a comprehensive examination of how law can be rationally binding. A descriptive theory of law, then, requires examining law’s normative foundations in ethics and politics. Legal positivism, by focusing on law as a socially recognised standard, tends to the view that a complete descriptive theory of law does not depend on examining law’s rationality. This methodological divergence arguably constitutes the main rift between the two traditions. 3. Motivating Natural Law Legal positivism is the dominant view in contemporary legal philosophy. It is so widely accepted that people sometimes find it hard to see what motivates the natural law position. Natural law, as we have seen, supplements (1) with (2). However, this move is unmotivated unless there is something important about law that (1) cannot capture. What, then, is the motivation for extending the necessary features of law beyond social sources? What aspects of law is legal positivism unable to explain? Natural law theory and legal positivism can both be viewed as attempts to explain and systematise what we might term the popular view of law: the beliefs ordinary people hold about law prior to systematic ref lection. Both schools of thought seek to make sense of two central aspects of the popular view. The first component is that lawisasetofsocialrules: it is a collection of normative standards accepted as binding by members of a community.