1. Diversity of terms in natural law
The term ‘natural law’ is used to describe a number of different historical phenomena. In searching for universally accepted and unalterable basic principles for a just and human law, they share a core common meaning. Over the centuries, the logic of natural law therefore became the benchmark and starting point of criticism of the existing law. But the particulars of its appearance vary considerably depending on what is understood by ‘nature’. It makes a difference, whether a term is teleologically charged, yet individually orientated (as in the works of Aristotle) or whether it comprises human nature as a whole (as in the world order ruled by Stoa logos). As purely earthly sphere, the notion of ‘nature’ in Christian medieval philosophies had no room for gods. Though the natural law of the Middle Ages perhaps reflects God’s plan, it was, unlike that of antiquity, always subordinate to a ius divinum. As opposed to Christian-scholastic philosophy, modern natural law is based on rational logic, later increasingly influenced by the enlightenment: nature, human nature and its social context are subjects which can be explored by progressive scientific examination. However, the term ‘natural law’ does not just lead to a periodization of legal history. In the Anglo-Saxon world, fundamental aspects of jurisprudence are debated and philosophized in its name, areas of legal normativity are explored, sometimes strongly coloured by deontic logic. The questions behind this concern the validity and positivity of the law and its relationship to morals or customs. They can be no less problematic in countries shaped by codification, but are often sidelined by the idea of a uniformly valid law, which tends to push them aside to the marginalized field of legal philosophy. In recent history and on several occasions, however, they have become topical also on the Continent: the debate on natural law experienced a surge after the end of World War II, as well as after 1989 in Germany during the so-called Berlin Wall Snipers’ Trials.
2. Natural law as an epoch
For European private law the above-mentioned early modern phase of natural law discourse was particularly significant. It illustrates a stream of thought found throughout Europe in the 17th and 18th centuries which, freed from the constraints of Christian moral theology, sought to define a proper structure for human order and created a new framework for the law; countless pieces of legal literature have been penned, and university chairs were created in its name.
Johannes Althusius has often been associated with so-called ‘early’ natural law. Its first authoritative advocate was the Dutchman Hugo Grotius, who presumed as its ethical starting point the human willingness to live together peacefully and as reasonable beings (socialitas). On that basis, he developed more specific, mostly contractually constructed principles. Thinkers such as Thomas Hobbes, Samuel von Pufendorf or Christian Thomasius then designed the comprehensive and classical systems of natural law. Samuel von Pufendorf, who taught in Sweden and Prussia, developed the system most important for the history of European private law. In contrast to Hugo Grotius, he took human weakness and indigence as its foundation (imbecillitas): a system of mutual aid emerges from this, constituting socialitas. Consequently, Pufendorf’s concept of natural law is primarily one of duty (officium), bound to humanity’s God-given destiny to serve, from which the law ensued. Starting with these foundations, and continuing in ‘late’ natural law, a social programme defined by reason was formed. It led to new, all-embracing and systematic codifications in central Europe. For example, the natural lawyers Christian Wolff and Daniel Nettelbladt and their school of thought had a direct and significant influence on the formulation of the Prussian code (Allgemeines Landrecht für die Preußischen Staaten (1794)).
The diversity of ideas in natural law over a period of nearly 200 years goes far beyond those of the scholars mentioned here. They can be seen throughout Europe and in many different forms, from absolutist-like concepts to liberal ideologies, such as that of John Locke. Locke gained exceptional influence over the Anglo-Saxon political ideal with his political doctrine, influenced by Calvinism and orientated towards earthly concepts of freedom and property. As a comprehensive social philosophy of modernity, natural law could be described as a kind of universal academic discourse (Franz Wieacker; Klaus Luig). Its real place, however, was in the field of law. Samuel von Pufendorf regarded himself as a law teacher expounding a contemporary new concept of law: law as a whole ought to be redesigned and re-established, independent of the learned doctrine of the early ius commune as well as moral theology. The attractiveness of this idea is perhaps also linked to the loss of authority of the Corpus Juris Civilis. In view of the criticism to which they had been subjected by the humanists (humanism), and also in the light of newly emerged European legal concepts such as individuality and subjectivity, the original Roman texts could no longer offer an authoritative model, necessitating a new way of legal thinking.
3. Secularization of legal thinking
The impact of natural law only becomes clear when seen against the history of its development. As religious division and confessional wars suddenly revealed a previously undreamt of need for guidance and pitted sovereign states with hostile faiths against each other, a new grounding of law became necessary, one that was capable of dispensing with elements of the ultimate foundation in theology. Hugo Grotius had already re-emphasized the search for the conditions of a peaceful coexistence and had looked for rules of law within society and between different peoples. Whilst his question of which law was binding should a God not exist was still indebted to the scholastic culture of quaestiones, Hobbes aimed for a fundamentally secular foundation of law, by providing a new definition of the role of the state as a legislative power. Apart from that, a new, equally secular, idea of human dignity emerged. It was seen as an individual right, derived from the secular presupposition of human equality, and constituted a mandate for the political legislator, especially in the work of Samuel von Pufendorf, and in the subsequent political discourse of the 18th century.
Natural law was also subject to an even more far-reaching change during the same period. As the idea of God as the creator of natural law became weaker, the latter not only increasingly appeared as a product of human rationality, but was also affected by the rise of positive law as a point of reference, or even as the first benchmark for legal thought. Since the early enlightenment period especially, a strong orientation in human legislation gained ground—in the work of Christian Thomasius to such an extent that he was even willing to reassign natural law to the sphere of ethics. This tendency reinforced and radicalized itself over the course of the 18th-century: law was increasingly seen as something created by man and thus at the same time narrowed down to the key idea of legislation. It reached its best-known expression as a euphoric utopia of human self-determination in revolutionary France in the Déclaration des droits de l’homme of 1789. For the natural lawyers themselves, a vision of law without God was never a proposition worth consideration, since for them all human existence had its origin in God and their philosophy was Christian. The growing marginalization of a religious basis in their theory of law and its emancipation from theology, however, meant that philosophers of the enlightenment such as Jean-Jacques Rousseau could also fall back on their philosophy of law.
4. Mos geometricus
The new theory of law also led to dramatic changes in private law. The most obvious effect on the modern structure of private law in Europe was the complete, methodical overhaul of legal scholarship. It attained a new understanding of how a legal system should be conceived as a system in itself and how it should be structured. In the 17th century, in the light of the rise of rationalism, this led to the idea that experiments with and observations of the natural laws could reveal a treasure of previously hidden insights also for the social sciences. The proper method of reasoning lay in a mathematics-like, logical deduction from given premises. While even Hugo Grotius already saw a connection between his teaching and the theoretical approach of mathematics, the famous methodological treatise of Réne Descartes (1637), with its rationalistic rejection of traditional metaphysics, had a great impact on the natural lawyers. The first system of natural law which could lay claim to being complete was tackled by Hobbes. Above all, however, it was Samuel von Pufendorf who established, in contrast to Hugo Grotius, an entire system of natural law, in which all norms were strictly derived from basic premises. Thus, he attempted to bring his explanations on contracts in line with certain higher principles from which every individual norm had to be deduced. For the culture of critical analysis of private law, the works of Christian Wolff and his school of thought later became particularly important in some parts of Europe. Wolff went far beyond Pufendorf’s degree of systematization and built his system consistently on syllogistic deductions, all of which were to be scrupulously deducted from the highest principles in his understanding of natural law. This ideal of geometrical or, as it were, pure method became part of the so-called conceptual jurisprudence of the 19th century and served as an ideal not just for formal but also for substantive coherence, even influencing the creation of the German Bürgerliches Gesetzbuch (BGB) in 1900. It stands in contrast to another idea of private law prevailing in Europe which, though equally influenced by natural law, remains closer to the Roman institutional tradition of private law. An example of this is the French Code civil of 1804.
5. Nationalization of private law
In view of the wide impact on natural law, this difference is not surprising. As in the case of the usus modernus and the elegant jurisprudence, the writings of natural lawyers show the contemporary phenomenon of growing national identities. In private law, an increasing number of national textbooks were published in which a particular sense of national identities is apparent. At the same time, the native languages of the individual nations made themselves heard in European scholarship, and Latin, which for centuries had been the lingua franca of European legal doctrine, began to lose its influence. Translations became essential, especially for the spread of natural law. The work of Jean Barbeyrac for example, who translated the writings of Samuel von Pufendorf into French and also provided a detailed commentary, became influential. However, the idea that the common European basis of the ius commune was pulled apart by the nationalization of natural law thinking is apt to distract from the fact that, simultaneously, natural law made a considerable unification of private law on a national and territorial level possible, and also helped to overcome the legal fragmentation in Europe’s regions. For the political ideals of natural law contributed to the centralization and monopolization of legislation by the individual national and territorial states. The best examples of this are the codifications in the German-speaking countries at that time, the Codex Maximilianeus Bavaricus Civilis (1756), the Prussian Allgemeines Landrecht für die preußischen Staaten (ALR) (1794), and the Austrian Allgemeines Bürgerliches Gesetzbuch (ABGB) (1811/12). They were not direct applications of natural law doctrines, but were strongly influenced by their terminology, structural ideals and concepts.
The success story of natural law is of course principally that of a Protestant development, taking place in northern Europe, first in Holland, Germany and Scandinavia, but also in the alpine countries, France and England. In Italy, works which fell under suspicion of subversion by the clergy were slower to make an impact. Absorption of the new teachings on the Iberian Peninsula was also hesitant as, in contrast to the teachings of the Spanish late scholastics, they seemed to have the disadvantage of having a secular character. In England on the other hand, the political discourse on natural law and enlightenment had wide repercussions, though the effect of a mos geometricus in law remained, in view of England’s own legal traditions, comparatively small. William Blackstone’s writings, as well as many contemporary judgments do, however, show some influence. A more comprehensive absorption of natural law systematization in the common law' occurred later in the 19th century. Natural law experienced a particularly selective reception in the American independence movement, eg in the works of Thomas Jefferson. These works go back to the politically liberal, enlightened doctrines of natural law as well as Samuel von Pufendorf’s writings, whilst leaving no doubt as to the divine foundation of Jefferson’s understanding of natural law and his commitment to the Bible.
6. New forms for European private law
Natural law’s innovations also gained influence in core areas of private law, far beyond the reaches of northern Europe and in many different forms. The best known examples show that this influence shaped legal terms without which current private law doctrine would be difficult to imagine. For example, given the contractually focused foundations of natural law, general contract doctrine in private law received a boost. The contract, resting upon mutual recognition, became a general foundation of legal relations and thus gained central importance. In the work of Samuel von Pufendorf many questions of contract law were thoroughly analysed. He not only dispensed with the old Roman contract categories but also tackled the idea of synallagma, a categorization of main and ancillary obligations, the notion of a causa, and other characteristics of general contract doctrine. A similar extension of general categories can be seen in other legal concepts; thus the general notion of negotium established itself as the basis of the doctrine of the judicial act. Beyond the interpretation doctrines of the ius commune, the declared will of a party became a cornerstone of legal analysis (interpretation of contracts, mistake). In the same way, the moment of a contract’s conclusion itself was subjected to doctrinal analysis. Whilst the expansion of the concept of an obligation by the natural lawyers was more a deepening of previous knowledge than a discovery, the reflections on the foundation and scope of non-contractual liability led much further. In delict/tort law (law of torts/delict, general and lex Aquilia), the natural law doctrines, based on the idea of duty, focused on the unlawful act as a basic category and, as a result, a general liability clause emerged as well as a clearer system. One particularly important event, which had an impact first on German private law but also on international scholarship, was the development of a general part. This meant that a set of general rules was conceptualized, applicable to all specific areas of private law, thereby guaranteeing a coherent system. It was developed in Christian Wolff’s school of thought, but was later continued outside the field of natural law. Throughout Europe, however, contemporary doctrines on the transfer of movable goods in their various shapes had a strong and lasting impact on the national legal systems.
In some cases, such as the one just mentioned, it is not certain that we are dealing here with a specifically natural law influence. The epoch of natural law was part of the general development of scientific differentiation of European private law, which continued over centuries and which was driven by a variety of intellectual and economic forces. The development of a systematic contract doctrine, for example, can be traced back to the Spanish late scholastics (James Gordley); other concepts can be traced back even further. Natural law absorbed all of them, as even the formation of natural law philosophy itself can be understood as a result of the legal discourse which took place on the threshold of the modern age (Merio Scattola). In view of the blurred boundaries of usus modernus and natural law and the various interactions between the two, the history of private law cannot always differentiate clearly between them. This is not surprising. Usus modernus itself was more focused on legal practice and finding appropriate solutions to contemporary legal problems, whereas natural law gave it a kind of conceptual-philosophical framework; both paved the way towards modern private law.
James Gordley, The Philosophical Origins of Modern Contract Doctrine (1991); Tony Weir (tr), Franz Wieacker, A History of Private Law in Europe (1995) 227 ff; Peter Stein, ‘The Quest for a Systematic Civil Law’ (1995) 90 Proceedings of the British Academy 147; Otto Dann and Diethelm Klippel (eds), Naturrecht—Spätaufklärung—Revolution (1995); Klaus Luig, Römisches Recht, Naturrecht, nationales Recht (1998); Klaus Luig‚ ‘Vernunftrecht’ in Handwörterbuch zur deutschen Rechtsgeschichte vol V (1998) 781; Merio Scattola, Das Naturrecht vor dem Naturrecht. Zur Geschichte des ‘ius naturae’ im 16. Jahrhundert (1999); David J Ibbetson, ‘Natural Law and Common Law’ (2001) 5 Edinburgh Law Review 4; Jan Schröder, Recht als Wissenschaft. Geschichte der juristischen Methode vom Humanismus bis zur historischen Schule, 1500–1800 (2001); Diethelm Klippel (ed), Naturrecht und Staat. Politische Funktionen des europäischen Naturrechts (2006); Lorraine Daston and Michael Stolleis (eds), Natural Law and Laws of Nature in Early Modern Europe (2008).
Hugo Grotius, De Jure Belli ac Pacis Libri Tres, in quibus Jus Naturæ & Gentium, item Juris Publici præcipua explicantur, vol 1 (1913); Francis W Kelsey (tr) vol 2 (1925); G Mascovius (ed), Samuel Pufendorf: De jure naturae et gentium libri octo (1967); Marcell Thomann (ed), Christian Wolff: Gesammelte Werke, vol 2/26: Institutiones juris naturae et gentium (1969); Christian Thomasius, Fundamenta iuris naturæ et gentium ex sensu communi deducta (reprint of the 4th edn, 1718) (1979); Howard Warrender (ed), Thomas Hobbes: De Cive. (1983); James Tully (ed), Michael Silverthorne (tr), Samuel Pufendorf: On the Duty of Man and Citizen According to Natural Law (1991); Richard Tuck and Michael Silverthorne (eds, trs), On the Citizen (1998).