An Enquiry Concerning Human Understanding is a 1748 work by David Hume. It is often known as the First Enquiry, as distinguished from the Enquiry Concerning the Principles of Human Morals. Both works provide succinct accounts of aspects of the philosophy originally developed in Hume's Treatise on Human Nature.
The opening sections of the Enquiry offer a theory of knowledge which owes much to Locke, while making a clearer distinction between sense impressions and ideas. Hume's more fundamental departure was his conclusion that there was no rational justification for our making judgements about the world based on cause and effect, and that we do so simply out of custom and habit.
In the latter part of the book, Hume applied his scepticism to a variety of metaphysical and religious beliefs, concluding however with a chapter recommending the approach of the more moderate Academic sceptics among the ancients, rather than that of the more radical Pyrrhonians.
He ends with a paragraph whose precise significance, as a criterion of truth or of meaningfulness, has been much debated by later analytic philosophers:
When we run over libraries, persuaded of these principles, what havoc must we make? If we take in our hand any volume; of divinity or school metaphysics, for instance; let us ask, Does it contain any abstract reasoning concerning quantity or number? No. Does it contain any experimental reasoning concerning matter of fact and existence? No. Commit it then to the flames: for it can contain nothing but sophistry and illusion.
Free online texts
Early Modern Texts: An Enquiry Concerning Human Understanding, adapted and translated into modern English, by Jonathan Bennett. PDF format.
Gutenberg: An Enquiry Concerning Human Understanding. Multiple formats.
Internet Archive: An Enquiry Concerning Human Understanding, and Selections from A Treatise of Human Nature (1907). Multiple formats.
Internet Archive: An Enquiry Concerning Human Understanding, with works by Locke and Berkeley. (Great Books of the Western World edition, 1937). Multiple formats.
University of Adelaide (Internet Archive): An Enquiry Concerning Human Understanding. Multiple formats.
Wikisource: An Inquiry Concerning Human Understanding. HTML and other formats.