Hume, David (1711–76)
Authors: Garrett Don 
Published: September 2018

David Hume, one of the most prominent philosophers of the eighteenth century, was an empiricist, a naturalist and a sceptic. His aim, as stated in his early masterpiece, A Treatise of Human Nature (written and published when he was in his twenties), was to develop a ‘science of man’ – what would now be called a cognitive and conative psychology – that would provide a philosophical foundation for the sciences, both those that concern human life (such as ‘logic, morals, criticism, and politics’) and those that are merely investigated by human beings (such as ‘mathematics, natural philosophy, and natural religion’). Although the Treatise itself received relatively little attention upon its publication in 1739–40, Hume’s philosophical views attracted greater attention as a result of An Enquiry concerning Human Understanding (1748), An Enquiry concerning the Principles of Morals (1751), various essays and his posthumously published Dialogues concerning Natural Religion (1779). He was also noted as a historian, diplomat and essayist on political and economic topics.
One aspect of Hume’s empiricism was methodological, consisting in his endorsement and practice of ‘the experimental method’ requiring that claims in his science of man be derived from and supported by experience rather than from intellectual ratiocination independent of experience. In this, he saw himself as following in the tradition of Locke and as standing against the excesses of earlier philosophers such as Descartes. But whereas natural philosophers (that is, natural scientists) such as Newton could simply design experiments to answer questions about the behaviour of bodies in particular circumstances, the premeditation of attempts to place the mind in a particular situation could alter the mind’s natural operations, he maintained, so that, as he states in the Introduction to the Treatise, we must ‘glean up our experiments in this science from a cautious observation of human life, and take them as they appear in the common course of the world, by men’s behaviour in company, in affairs, and in their pleasures’. Another aspect of his empiricism was conceptual, consisting in his doctrine – itself defended through use of the experimental method – that all ideas, and hence all concepts, must be copied from ‘impressions’, that is, sensory or internal experiences. He thus also followed Locke in rejecting Cartesian ‘innate ideas’.
Hume’s pursuit of the experimental method proved, in his conduct of it, to support his methodological empiricism as well; for he claimed to find that all beliefs concerning ‘matters of fact and real existence’ – as distinguished from pure ‘relations of ideas’ such as mathematics – depend on the relation of cause and effect, and that relations of cause and effect, in turn, can only be discovered through the observed constant conjunction of events of one type with events of another type. Yet although we (philosophers included) easily suppose that we perceive a ‘necessary connexion’ binding an effect to its cause in such a way that it would be a contradiction for the one not to follow the other, there is in fact no such contradiction; for a cause and its effect are always two distinct events, either of which can be conceived to occur without the other. The attribution of a ‘necessary connexion’ to causes and effects results from the mind’s projection onto them of its own feeling of mental determination to make an inference from the occurrence of an event of the one type to an event of the other after experience of their constant conjunction. Such inferences are not themselves founded on any process of reasoning concerning the uniformity of nature, for the denial of the uniformity of nature is not contradictory, and any attempt to defend the uniformity of nature by appeal to past experience would assume what the reasoning was supposed to establish. Instead, they are based on the mental mechanism of ‘custom or habit’. While he endorses – and engages in – reasoning, Hume finds that many operations of the mind, including those involved in volition and morals, owe less to reason and more to other features of the mind’s operations than might have been supposed.
Hume’s naturalism consisted in his determination to treat the human mind as a part of nature, equally susceptible to scientific investigation and equally subject to ordinary causal laws, without invoking either special natural properties or supernatural entities. Indeed, he emphasized the extent to which human mental operations resemble those of animals. He was a determinist concerning both physical and mental events, holding that a given set of circumstances will always produce the same outcome in accordance with uniform laws of nature. Unlike Spinoza, however, he held this doctrine only because he thought it was supported by experience as a likely extrapolation from the successes of scientific enquiry. His naturalism is evident in his treatment of morals, which he explains as deriving from the human ‘moral sense’ – that is, the capacity to feel a distinctive kind of approbation and disapprobation when considering features of character – that is, activated primarily by natural sympathy with those who are affected by the character traits in question. Virtue and vice acquire their central role in human life primarily through their ability to inspire love and pride, hatred and humility. Hume did not ever explicitly deny the existence of a deity, and he allowed that the hypothesis of an intelligent cause for the universe has a natural persuasive force. However, he forcefully criticized arguments for the existence of God, for religious miracles, for an afterlife with rewards and punishments, and for a deity’s moral goodness or moral concern. He regarded religion as being largely pernicious for both enquiry and morals.
Hume did not use the terms ‘empiricist’ or ‘naturalist’. He did, however, call himself a sceptic. His scepticism was the consequence of his discovery, in the course of his investigations, of the many ‘infirmities’ of human cognitive nature, including its inability to defend by reasoning many of its own most fundamental operations. While he held that intense consideration of these infirmities can produce a state of extreme but temporary doubt and bewilderment, the scepticism that he endorsed and sought to practice was ‘mitigated’ in degree, consisting in a certain diffidence and lack of dogmatism in all of his judgments. In addition to this general mitigated scepticism, however, he also recommended a complete suspense of judgment concerning matters entirely beyond our experience – such as cosmological speculation concerning ‘the origins of worlds’.