Tindal.48 Rather, Turnbull’s pamphlet is intellectually significant because it underlines his debt to Samuel Clarke’s blend of rational Christianity and moderate Enlightenment.
Turnbull’s indebtedness to Clarke resurfaced in his last pamphlet, An Impartial Enquiry into the Moral Character of Jesus Christ (1740). Turnbull elaborated on Clarke’s assertion that Christ’s spotless character showed that he was “neither an Imposter nor an Enthusiast,” and that Jesus’ moral integrity “add[s] great Weight and Authority to his Doctrine, and make[s] his own Testimony concerning himself exceedingly credible.”49 Using the epistolary form, Turnbull addresses himself to a Deist and endeavors to persuade this imaginary friend that Christ was an even greater teacher of morality than Socrates and that Christ’s exemplary behavior and good works attested to his divine mission. Turnbull was implicitly arguing that Christ’s unimpeachable character and his miracles constitute “extrinsic” evidence for the truth of Christianity which complements the “intrinsic” evidence derived from the excellence of his teachings. Together, this evidence suffices to persuade the candid unbeliever of the reasonableness of Christian belief.50 With the Impartial Enquiry (and The Principles of Moral and Christian Philosophy), therefore, Turnbull’s protracted dialogue with Deism and his public defense of the reasonableness of Christianity (and hence of the moderate Enlightenment) came to an unresolved end.
Turnbull’s apologetic agenda in his writings on religion was set while he was a student in Edinburgh. His Aberdeen graduation theses, which document
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the transformation of the curriculum at Marischal College in the 1720s, likewise show that his teaching reflected his studies at the University of Edinburgh and his conversations in the Rankenian Club.51 The theses demonstrate that much like his colleagues he was conversant with a wide range of ancient and modern writers and that he incorporated the ideas of Bacon, Descartes, Locke, and Newton into his lectures. But the theses also indicate that his courses differed significantly from those of the other regents. First, his topics for student disputations contain little on metaphysics and logic, which suggests that he limited the time spent on these subjects. It seems, therefore, that he went further than some of his colleagues in removing scholastic remnants from the curriculum. Second, as noted, the theses reveal his preoccupation with countering the threat of irreligion. Such apologetics was by no means novel, for the primary aim of a university education was to inculcate sound moral and religious principles. The formulation of his argument was, however, original because he relied exclusively on the argument from design to refute atheism and he blended Newton’s theocentric vision of the physical universe with Shaftesbury’s conception of a benevolent natural and moral order to illustrate the design in nature.52 Third, the disputation topics set in 1726 imply that his teaching of ethics and politics was framed in terms of the natural law tradition. Regents in the two Aberdeen colleges had drawn on the writings of Grotius and Pufendorf from the latter part of the seventeenth century onward, but it was Turnbull (along with his fellow regent at Marischal David Verner) who did most to recast the study of moral philosophy in the mold of natural law.53 Last, Turnbull was the first Scottish regent or professor to state explicitly that moral philosophy ought to be studied using the same method as that employed by Newton in natural philosophy. Much had been made
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in the natural law tradition of the methodological unity of the two main branches of philosophy, and there is little doubt about Turnbull’s debt to Grotius, Pufendorf, and Richard Cumberland in this regard. Nevertheless, his 1723 thesis struck a new note when he appealed to Query 31 of Newton’s Opticks to justify his claim that the moral realm ought to be investigated empirically using the methods of analysis and synthesis.54 Turnbull was thus an early promoter of the Newtonian form of scientism adopted by successive generations of moralists not only in Aberdeen but throughout the European Enlightenment more generally.55
Like the Edinburgh virtuosi who shaped the early Scottish Enlightenment, Turnbull believed that all branches of human learning formed a coherent and unified system which he likened to a tree of knowledge.56 This view underwrote his belief in the methodological unity of the natural and moral sciences, and it also enabled him to delineate the cognitive relations between his historical and antiquarian interests and his broader philosophical concerns. His fascination with history and Roman antiquities was something that he probably originally shared with his fellow Rankenian Charles Mackie. At Edinburgh (and elsewhere) history was taught as an adjunct to law, so that for Turnbull and Mackie the study of these subjects was closely intertwined.57 Once Turnbull became a travelling tutor his taste for “the Study of the Antients” deepened, while his contacts with antiquarians and historians in London turned his researches in new directions.58 His work on antiquities and history was also deeply influenced by French models, as seen in his Three Dissertations and his edition of Justin.59 These late works register his indebtedness to the critical scholarship championed
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by the Parisian Académie des Inscriptions et Belles-Lettres and to the rationale for the study of history articulated by the noted historian and pedagogue Charles Rollin. The Three Dissertations pays tribute to Richard Mead’s collection: one of the engravings Turnbull included illustrates the celebrated ancient painting owned by Mead that was taken to portray Augustus, Agrippa, Maecenas, and Horace, while the other depicts a bas relief of actors and a musician that had recently been uncovered in Rome, which Turnbull believed was worthy of Mead’s ownership.60 Two of the three essays which he translated from the Histoire et mémoires de l’Académie des inscriptions et belles lettres discussed antiquarian topics related to these engravings. The third described the notable collection of paintings and statues amassed in ancient Rome by the infamous Gaius Verres. Turnbull used this essay as a vehicle to state what he believed were the proper ends of collecting the remains of the past. According to Turnbull, true collectors like Mead sought to benefit the public by opening up their cabinets to foster “the ambition to excel in the Arts of Design” and to promote “the Study of polite Literature” among their fellow citizens. But in Britain their efforts to arouse the “natural Genius” of the nation were sadly hampered by the lack of institutions comparable to the state and provincial academies in France. Turnbull here echoed a common complaint among men of letters that the British government did far too little to foster the advancement of learning.61
Turnbull’s discussion of the value of historical knowledge in the preface to his edition of Justin’s History complements his extended treatment of the topic in his Observations upon Liberal Education.62 As in the Observations, he paid tribute to Rollin’s achievements as a historian and apologist for the study of history and, following Rollin and the humanist tradition, emphasized that historical knowledge is valuable insofar as it can be used to teach moral and political lessons.63 This view of the primarily didactic
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function of history—what has come to be known as “exemplar history”—is encapsulated in Lord Bolingbroke’s dictum “that history is philosophy teaching by examples how to conduct ourselves in all the situations of private and public life.”64 For Turnbull civil history was thus the grounding for ethics and politics just as natural history was for natural philosophy. Moreover, he insisted that the facts of both branches of history illustrate broader moral and religious principles, and it was the recognition that the facts serve such higher ends that for him distinguished the true historian and antiquary from those who were guilty of mere “cockle-shellship,” that is, the random stockpiling of objects and information with no eye for their meaning.65
Turnbull’s Treatise on Ancient Painting explored another facet of his tree of knowledge, namely the connection between philosophy and oratory, poetry, and painting. His discussion hinged on his claim that painting is a language that can be employed to express the truths discovered in the moral and natural sciences.
