From 1746, Hume served for three years as Secretary to a distant relative, Lieutenant-General St. Clair, including as an aide-de-camp on diplomatic missions in Austria and Northern Italy, and even at one point as a staff officer on an ill-fated military expedition as part of the War of the Austrian Succession. It was during this period that he wrote his “Philosophical Essays Concerning Human Understanding”, later published as “An Enquiry Concerning Human Understanding”, which proved little more successful than the “Treatise”. He was charged with heresy (although he was defended by his young clerical friends, who argued that, as an atheist, he was outside the Church’s jurisdiction), and was again deliberately overlooked for the Chair of Philosophy at the University of Glasgow.
In 1752, the Faculty of Advocates employed him as their librarian, for which he received little or no emolument, but which gave him access to a large library, and which enabled him to continue historical research for his “History of Great Britain”. This enormous work, begun in 1745 and not completed until 1760, ran to over a million words and traced events from the Saxon kingdoms to the Glorious Revolution. It was a best-seller in its day and became the standard work on English history for many years. Thus, it was as a historian that Hume finally achieved literary fame.
From 1763 to 1765, Hume was Secretary to Lord Hertford in Paris, where he was admired by Voltaire and was friends (briefly) with Jean-Jacques Rousseau. For a year from 1767, he held the appointment of Under Secretary of State for the Northern Department in London, before retiring back to Edinburgh in 1768.
He died in Edinburgh on 25 August 1776, aged 65, probably as a result of a debilitating cancer he suffered from in his latter years, and was buried, as he requested, on Calton Hill, overlooking his home in the New Town of Edinburgh. He remained to the end positive and humane, well-loved by all who knew him, and he retained great equanimity in the face of his suffering and death.
Most of Hume’s philosophical work dates from his earlier years, in particular stemming from a mysterious intellectual revelation he appears to have experienced at the age of just eighteen. He spent most of the next ten years frantically trying to capture these thoughts on paper, resulting in “A Treatise of Human Nature” which he completed in 1737 at the age of just 26 (and published two years later). This book, which he subtitled “An Attempt to Introduce the Experimental Method of Reasoning into Moral Subjects”, is now consider to be Hume’s most important work and one of the most important books in the whole of Western philosophy, despite its poor initial reception. He refined the “Treatise” in the later “Philosophical Essays Concerning Human Understanding” (actually published as “An Enquiry Concerning Human Understanding” in 1748), along with a companion volume “An Enquiry Concerning the Principles of Morals” (1751), although these publication proved hardly more successful in the original “Treatise” on which they were based.
Hume was a thorough-going Empiricist, the last chronologically of the three great British Empiricists of the 18th Century (along with John Locke and Bishop George Berkeley), and the most extreme. He believed that, as he put it, “the science of man is the only solid foundation for the other sciences”, that human experience is as close are we are ever going to get to the truth, and that experience and observation must be the foundations of any logical argument. Anticipating the Logical Positivist movement by almost two centuries, Hume was essentially attempting to demonstrate how ordinary propositions about objects, causal relations, the self, etc, are semantically equivalent to propositions about one’s experiences.
He argued that all of human knowledge can be divided into two categories: relations of ideas (e.g. mathematical and logical propositions) and matters of fact (e.g. propositions involving some contingent observation of the world, such as “the sun rises in the East”), and that ideas are derived from our “impressions” or sensations. In the face of this, he argued, in sharp contradistinction to the French Rationalists, that even the most basic beliefs about the natural world, or even in the existence of the self, cannot be conclusively established by reason, but we accept them anyway because of their basis in instinct and custom, a hard-line Empiricist attitude verging on complete Skepticism.
But Hume’s Empiricism and Skepticism was mainly concerned with Epistemology and with the limits of our ability ot know things. Although he would almost certainly have believed that there was indeed an independently existing world of material objects, causally interacting with each other, which we perceive and represent to ourselves through our senses, his point was that none of this could be actually proved. He freely admitted that we can form beliefs about that which extends beyond any possible experience (through the operation of faculties such as custom and the imagination), but he was entirely skeptical about any claims to knowledge on this basis.
Central to grasping Hume’s general philosophical system is the so-called “problem of induction”, and exactly how we are able to make inductive inferences (reasoning from the observed behaviour of objects to their behaviour when unobserved). He noted that humans tend to believe that things behave in a regular manner, and that patterns in the behaviour of objects will persist into the future and throughout the unobserved present (an idea sometimes called the Principle of the Uniformity of Nature). Hume argued forcefully that such a belief cannot be justified, other than by the very sort of reasoning that is under question (induction), which would be circular reasoning. Hume’s solution to this problem was to argue that it is natural instinct, rather than reason, that explains our ability to make inductive inferences, and many have seen this as a major contribution to Epistemology and the theory of knowledge.
Hume was a great believer in the scientific method championed by Francis Bacon, Galileo Galilei (1564 – 1642) and Sir Isaac Newton (1643 – 1727). However, the application of the problem of induction to science suggests that all of science is actually based on a logical fallacy. The so-called induction fallacy states that, just because something has happened in the past, it cannot be assumed that it will happen again, no matter how often it seems to happen. However, this is exactly what the scientific method is built on, and Hume was forced to conclude, rather unsatisfactorily, that even though the fallacy applies, the scientific method appears to work.
Closely linked to the problem of induction is the notion of causality or causation. It is not always clear how we know that something is actually caused by another thing and, although day always follows night and night day, there is still no causal link between them. Hume concluded that it is the mental act of association that is the basis of our concept of causation (although different commentators differ in their interpretation of Hume’s words on the matter, varying from a logical positivist interpretation to a skeptical realist or quasi-realist position).
Hume’s views on personal identity arose from a similar argument. For Hume, the features or properties of an object are all that really exist, and there is no actual object or substance of which they are the features. Thus, he argued, an apple, when stripped of all its properties (colour, size, shape, smell, taste, etc), is impossible to conceive of and effectively ceases to exist. Hume believed that the same argument applied to people, and he held that the self was nothing but a bundle or collection of interconnected perceptions linked by the properties of constancy and coherence, a view sometimes known as “bundle theory”, and one in direct opposition to Descartes’s “I think therefore I am” assertion.
Hume’s anti-Rationalism, however, was not confined to his theory of belief and knowledge, but also extended into other spheres, including Ethics. He asserted that “reason is, and ought only to be, the slave of the passions, and can never pretend to any other office than to serve and obey them”. Thus, he severely circumscribed reason’s role in the production of action, and stressed that desires are necessary for motivation, and this view on human motivation and action formed the cornerstone of his ethical theory. He conceived moral or ethical sentiments to be intrinsically motivating, and to be the providers of reasons for action. Thus, he argued, given that one cannot be motivated by reason alone (given that motivation requires the additional input of the passions), then reason cannot be behind morality. His theory of Ethics, sometimes described as sentimentalism, has helped to inspire various forms of non-cognitivist and moral nihilist ethical theories including emotivism, ethical expressivism, quasi-realism, error theory, etc.
In his “A Treatise of Human Nature”, Hume definitively articulated the so-called “is-ought problem”, which has since become so important in Meta-Ethics, noting that claims are often made about what ought to be on the basis of statements about what is. However, Hume pointed out, there are significant differences between descriptive statements (about what is) and prescriptive or normative statements (about what ought to be), and it is not at all obvious how we can get from making descriptive statements to prescriptive. In line with his ingrained Skepticism, he advised extreme caution against making such inferences, and this complete severing of “is” from “ought” is sometimes referred to as “Hume’s Guillotine”.
As an Empiricist, Hume was always concerned with going back to experience and observation, and this led him to touch on some difficult ideas in what would later become known as the Philosophy of Language. For instance, he was convinced that for a word to mean anything at all, it had to relate to a specific idea, and for an idea to have real content it had to be derived from real experience. If no such underlying experience can be found, therefore, the word effectively has no meaning. In fact, he drew a distinction between thinking (which concerns clear ideas which have a real source in experience) and just everyday talking (which often uses confused notions with no real foundation in experience).
This reasoning also led him to develop what has become known as “Hume’s Fork”. For any new idea or concept under consideration, he said, we should always ask whether it concerns either a matter of fact (in which case one should then ask whether it is based on on observation and experience), or the relation between ideas (e.g. mathematics or Logic). If it is neither, then the idea has no value and no real meaning and should be discarded.
Like Thomas Hobbes before him, Hume sought to reconcile human freedom with the mechanist (or determinist) belief that human beings are part of a deterministic universe whose happenings are governed by the laws of physics. Hume’s reconcilation of freedom and determinism (a position known as compatibilism) involves a more precise definition of Liberty (“a power of acting or not acting, according to the determinations of the will”) and Necessity (“the uniformity, observable in the operations of nature; where similar objects are constantly conjoined together”), and the argued conclusion that not only are the two compatible, but that Liberty actually requires Necessity. Furthermore, he argued that, in order to be held morally responsible, it is required that our behaviour be caused or necessitated.
Hume wrote a great deal on religion, although, due to the rather repressive religious climate of the day, he deliberately constrained his words (as it was, the Church of Scotland seriously considered bringing charges of infidelity against him). He never openly declared himself to be an atheist, and did not acknowledge his authorship of many of his works in this area until close to his death (and some were not even published until afterwards).
However, it is certainly true that, in works such as “An Enquiry concerning Human Understanding” (1748) and “Dialogues Concerning Natural Religion” (written between about 1750 and his death in 1776, and published posthumously in 1779), he attacked many of the basic assumptions of religion and Christian belief, and he found the idea of a God effectively nonsensensical, because there was no way of arriving at the idea through sensory data. Some consider it his best work, and many of his arguments have become the foundation of much of the succeeding secular thinking about religion. Having said that, though, it is likely that Hume was, true to his most basic inclinations, skeptical both about religious belief (at least as demanded by the religious organizations of his time) and of the complete Atheism of such contemporaries as Baron d’Holbach (1723 – 1789), and his position may best be characterized by the term “irreligious”.
Hume argued that it is impossible to deduce the existence of God from the existence of the world because causes cannot be determined from effects. Although he left open the theoretical possibility of miracles (which may be defined as singular events that differ from the established laws of Nature), he cautioned that they should only be believed if it were less likely that the testimony was false than that a miracle did in fact occur, and offered various arguments against this ever having actually happened in history.
He gave the classic criticism of the teleological argument for the existence of God (also known as the argument from design, that order and apparent purpose in the world bespeaks a divine origin – see the Arguments for the Existence of God section of the Philosophy of Religion page for more details), arguing that, for the design argument to be feasible, it must be true that order and purpose are observed only when they result from design (whereas, on the contrary, we see order in presumably mindless processes like the generation of snowflakes and crystals). Furthermore, he argued that the design argument is based on an incomplete analogy (that of the universe to a designed machine), and that to deduce that our universe is designed, we would need to have an experience of a range of different universes. Even if the design argument were to be successful, he questioned why we should assume that the designer is God, and, if there is indeed a designer god, then who designed the designer? Also, he asked, if we could be happy with an inexplicably self-ordered divine mind, why should we not rest content with an inexplicably self-ordered natural world?
When faced with Leibniz’s contention that the only answer to the question “why is there something rather than nothing?” was God, and that God was a necessary being with no need of explanation, Hume responded that there was no such thing as a necessary being, and that anything that could be conceived of as existent could just as easily be conceived of as non-existent. However, he was not willing to propose a convincing alternative answer to the riddle of existence, taking refuge in the argument that any answer to such a question would be necessarily meaningless, as it could never be grounded in our experience.
Hume’s Political Philosophy is difficult to pinpoint, as his work contains elements of both Conservatism and Liberalism, and he resisted aligning himself with either of Britain’s two political parties, the Whigs and the Tories. His central concern was to show the importance of the rule of law, and stressed, in his “Essays Moral and Political” of 1742, the importance of moderation in politics (particularly within the turbulent historical context of 18th Century Scotland). In general, he thought that republics were more likely than monarchies to administer laws fairly, but the important point for Hume was that society be governed by a general and impartial system of laws, based principally on the “artifice” of contract (Contractarianism). He supported freedom of the press; he was sympathetic to elected representation and democracy (when suitably constrained); he believed that private property was not a natural right (as John Locke held), but that it was justified because resources are limited; he was optimistic about social progress arising from the economic development that comes with the expansion of trade; and he counselled strongly against revolution and resistance to governments except in cases of the most egregious tyranny.
Although best known today as a philosopher, Hume also developed many of the ideas that are still prevalent in the field of economics, and Adam Smith, among others, acknowledged Hume’s influence on his own economics and Political Philosophy. Hume believed in the need for an unequal distribution of property, on the grounds that perfect equality would destroy the ideas of thrift and industry, and thus ultimately lead to impoverishment. He was among the first to develop the concept of automatic price-specie flow, and proposed a theory of beneficial inflation, which was later to be developed by John Maynard Keynes (1883 – 1946).
Hume was also famous as a prose stylist, and pioneered the essay as a literary genre, publicly engaging with contemporary intellectual luminaries such as Jean-Jacques Rousseau, Adam Smith, James Boswell (1740 – 1795), Joseph Butler (1692 – 1752) and Thomas Reid (1710 – 1796).
But it was as a historian that Hume finally achieved literary fame. His immense 6-volume “History of England” (subtitled “From the Invasion of Julius Caesar to the Revolution in 1688”), written between 1745 and 1760, is a work of immense sweep, running to over a million words. It became a best-seller in its day and became the standard work on English history for many years.