"An idea assented to feels different from a fictitious idea, that the fancy alone presents to us: and this different feeling I endeavour to explain by calling it a superior force, or vivacity, or solidity, or firmness, or steadiness."
— Hume, David (1711-1776)
David Hume, A Treatise of Human Nature. Being an Attempt to Introduce the Experimental Method of Reasoning into Moral Subjects. 3 vols. (London: Printed for John Noon, 1739; Thomas Longman, 1740). <Link to ESTC><Link to ECCO><Link to ECCO-TCP><Link to OLL>
Reading David Hume, A Treatise of Human Nature, eds. D. F. and M. J. Norton (Oxford: OUP, 2000). Searching in Past Masters and OLL editions.