David Hume’s An Enquiry Concerning Human Understanding is a prominent work of Enlightenment philosophy, and one of the most influential texts on epistemology and human nature. The work underwent numerous revisions during Hume’s lifetime; it was published posthumously in its final form in 1777, the year after Hume’s death. This study guide uses the Oxford World’s Classics edition, edited by Peter Millican and published by Oxford University Press in 2007.

Summary

Hume sets up his investigation as one into moral philosophy, which he defines as “the science of human nature” (3); he signals to his readers that he will treat human behavior as it presently exists. An Enquiry… is not a work of ethics nor philosophical anthropology; rather, it explores the workings of the human mind—especially in relation to how human beings come to acquire knowledge about the world around them.

Hume begins by describing various kinds of philosophy and says that the pursuit of accuracy and perfection is desirable in all fields of knowledge. While many would prefer philosophical inquiry and its solutions to be clear and simple, complex methodology and argumentation are necessary for true conclusions. Hume makes distinctions between thoughts, ideas, and impressions. He speaks about how various ideas are related, as well as the nature of the relationship between what is commonly known as cause and effect.

In Chapters 5 and 6, Hume takes up the topic of skepticism. He says that human experience pushes us to infer an intrinsic and necessary connection between objects and events, but that the most we can infer is that there is an association between them, rather than a causal relationship. Hume argues that reason alone would not allow the conclusion that cause and effect are real; that conclusion only comes from subjective experience.

All knowledge, says Hume, is based in experience. In the first few chapters, he explores how our senses receive impressions, and how these impressions eclipse our thoughts and ideas in importance and vividness. Experience provides knowledge, Hume says; our inferences are made through experiences, not reason. Hume expands on this in Chapters 8 and 9, referring to the ability of lower, subrational animals who make inferences and judgments like people do, even outperforming children who have not yet reached the age of reason.

The final three chapters explore the possibility of miracles and the supernatural. Hume says that since all knowledge is based on experience, and that our general experience is that the world works in a very particular, logical, and steadfast manner, miracles are impossible. If our experience tells us that the world works in one specific way, then this experience rules out the possibility of the world working to the contrary. Knowledge of cause and effect is a recognition of patterns established over a long period of time; this proves the supernatural to be untenable.

Hume determines that, while intense doubt that questions one’s own existence is completely unhelpful, moderate skepticism is a necessary mode of rational thought and the only reasonable way of going through life. While the great majority of people will believe anything and become subject to any dogma or superstition that strikes their fancy, the philosopher—the reasonable person—will navigate the middle path through extremes with modesty and ease.

The only thing that can’t be submitted to skeptical inquiry is mathematics, which deals with quantities and numbers. Every other kind of knowledge enters the realm of human knowing through the senses and impressions of the world gained through experience.