"It is remarkable concerning the operations of the mind, that, though most intimately present to us, yet, whenever they become the object of reflection, they seem involved in obscurity; nor can the eye readily find those lines and boundaries, which discriminate and distinguish them."
— Hume, David (1711-1776)
First published as Philosophical Essays Concerning Human Understanding (London: Printed for A Millar, 1748). <Link to ECCO><Link to ECCO-TCP><Link to 1748 edition in Google Books> "Second edition" in 1750, "third edition" in 1756. First titled An Enquiry Concerning Human Understanding in 1758.
In ECCO-TCP, see also Essays and Treatises: on Several Subjects. By David Hume, Esq, 4 vols. (London: Printed for A. Millar; and A. Kincaid and A. Donaldson, at Edinburgh, 1760). <Link to vol. III>
Text from David Hume, Enquiries Concerning Human Understanding and Concerning the Principles of Morals. 3rd edition. Ed. L. A. Selby-Bigge; P. H. Nidditch (Oxford: Oxford University Press, 1975). Note, Nidditch reproduces the the second volume of the posthumous edition of 1777, which he has collated with the preceding 1772 edition.