These individuals formed a tight-knit group who met in the clubs of Edinburgh, Glasgow, and Aberdeen: clubs like the Select Society, the Poker Club, the Oyster Club, the Aberdeen Wise Club, the Glasgow Literary Society, and the Political Economy Club, where they heard papers and discussed the latest publications in philosophy and science. Many of these clubs, like the Edinburgh Society for Encouraging Arts, Sciences, Manufactures, and Agriculture, which later became the Royal Society of Edinburgh, were set up to apply scientific knowledge to practical improvement.
The latest ideas from England and Europe were absorbed and debated along with the latest Scottish ideas. The Scots corresponded with and met the leading thinkers of the time as part of a cosmopolitan intellectual environment. Enlightened visitors to Scotland such as Ireland’s Edmund Burke and America’s Benjamin Franklin (1706–90) were welcomed into a ferment of intellectual debate. Indeed, Tobias Smollett described the Scotland of this time as a hotbed of genius. Thinking about Adam Smith as moving in this context is helpful to us, as we can see the thinkers whose ideas influenced the development of his thought and those with whom he interacted in the discussion clubs of Enlightenment Scotland. Understanding Smith as a man of the Enlightenment, and particularly as a man of the Scottish Enlightenment, helps us to grasp a number of centrally important themes in his work: the most important of these being his commitment to science.
Newton
Perhaps the greatest inspiration for the Enlightenment was Sir Isaac Newton (1642–1727). Newton’s towering achievements in the natural sciences made him the template for the successful public intellectual. Voltaire heaped praise on him as supplanting the thought of René Descartes (1596–1650), and his fame became such that he was even lauded in poetry by Alexander Pope (1688–1744). Newton’s heroic status rested on his refinement of the scientific method first mooted by Francis Bacon (1561–1626). The method was grounded on the importance of observation and the generation of simple general rules of cause and effect based on the regularities observed in nature. This method avoided the error of Descartes, whose search for first principles led him to theorize beyond what the evidence supported.
Newton’s Principia Mathematica (1687) popularized a new understanding of what science was and what we could expect from it. The Newtonian, or experimental, method also had a further decisive advantage over its rivals: it provided testable predictions. French expeditions to Peru in 1735 and to Lapland in 1736 appeared to confirm Newton’s description of the shape of the earth, while the reappearance of Halley’s Comet in 1758 again demonstrated the success of his ideas. Colin Maclaurin (1698–1746) popularized Newton’s work in the Scottish universities, ensuring that the young Scots whom he taught had the opportunity to experience cutting-edge science. By the time Smith was a student, the spirit of Newtonianism had become deeply embedded in the curriculum.4
Another major contributor to the modern science that Smith absorbed was John Locke (1632–1704). Locke’s writings on education and on the theory of knowledge became a staple part of the understanding of psychology during the Enlightenment. Locke argued that all knowledge was based on experience and observation. He rejected the idea that human minds came stocked with innate ideas. Instead humans arrive with a tabula rasa or clean slate, and then proceed to build the content of their minds through experience of the world. All of our ideas arise from sense perceptions or as the result of reflection on sense perceptions and come to form increasingly complex thought processes. In terms of education, this led Locke to stress the importance of socialization and the need to state ideas in as plain and straightforward a fashion as possible.
Hume
The ideas of Newton and Locke form the backdrop to the thinking of the man who is the single most important influence on Adam Smith’s thinking: David Hume. Hume came from a very similar background to Smith and, being around a decade older, had already passed through the Scottish university system and written his first great work, the Treatise of Human Nature, by the time Smith was at Oxford in the 1740s. In Hume’s hands, the logic of the experimental method and the Lockean theory of ideas were pressed inexorably to their sceptical conclusions: the idea ultimately being reached that we must accept that all human knowledge is based on conditional probabilities acquired from experience by induction. In other words, there could never be any definitive ‘proof’ or truth outside systems of human concepts such as mathematics.
Hume begins the Treatise by noting that science is plagued by excessive abstraction and dedication to systems of thought. The only response to disputes between the adherents of these different systems of thought is recourse to empirical evidence. For Hume, all science is based on human understanding, and so all science must be based on a secure understanding of how human beings understand: on what he called the science of man. In turn, the only secure basis for such a science of man is experience and observation. Like natural scientists, we must conduct experiments and generalize from them. But experiments in the science of man cannot be the same as experiments in the natural sciences: we cannot manipulate people in the same way we mix chemicals. For Hume, we must instead have recourse to the observation of human life as it is and as it has been lived by actual people. If we look for examples and then compare them, we will gradually be able to build a picture of what is universal in human experience. The evidence that this provides us with will give insight into what motivates human behaviour and how humans think. Crucially for the development of the ideas of Smith and the Scottish Enlightenment, this led to the view that history was the data for a science of society.
The most controversial part of Hume’s Treatise is his deconstruction of how humans come to make connections between the ideas that they draw from experience. Perhaps the easiest way to understand his position is to trace his basic understanding of the core scientific idea of cause and effect. Hume sets out to understand how humans make connections between phenomena. His answer is to say that we attribute the relationship between two phenomena to be one of causation – that one thing causes another. Hume then breaks down the steps in how we form that sort of belief. He argues that we draw on our experience of the world to observe that the two phenomena are closely connected, that one of them precedes the other, and that they have always been found this way. In the classic example, one billiard ball strikes another and so ‘causes’ the movement of the second ball. Hume says that this leads us to form a belief that there is a ‘necessary connexion’ between the two. So far this is similar to Locke’s theory, but it is where Hume goes next that built his reputation as a sceptic. Hume argues that this form of knowledge is based on habit rather than reason.
Hume wants to understand why we think like this. The first thing to note is that we come to believe that the two events are connected because there have been repeated cases in our experience where they have been. The evidence of our senses is corroborated by multiple examples. But then Hume raises the question of why we assume that future cases will always be like past cases. His answer is that we believe this because we form beliefs based on custom and habit rather than demonstrative reason. Knowledge and expectations are based on induction from past experience. Humans believe that the world will continue as it has always done, that there is a ‘necessary connexion’ between two phenomena that are always found together; but the key point is that we cannot prove this through detached philosophical reasoning.
Hume’s point is that constant conjunction from past experience can allow us to believe that the sun will rise tomorrow as it rose today, but we cannot provide any definitive proof that this will be the case. If our knowledge of nature is based on generalization from past experience, we can never reach absolutely certain knowledge about the future. Instead we can develop increasingly sophisticated descriptions of past behaviour that we assume will allow us to understand the future, but such beliefs rest on probability rather