"Our simple ideas, and even our complex ideas, and notions return sometimes of themselves, we know not why, nor how, mechanically, as it were, uncalled by the mind, and often to the disturbance of it in the pursuit of other ideas, to which these intruders are foreign."
— St John, Henry, styled first Viscount Bolingbroke (1678-1751)
(Essay I, §2; vol. iii, pp. 367-8).
See "Letters or Essays Addressed to Alexander Pope, Esq." in the third volume of David Mallet's The Works of the Late Right Honorable Henry St. John, Lord Viscount Bolingbroke, 5 vols. (London : [s.n.], Printed in the Year 1754). <Link to ESTC><Link to ESTC>
Text from the third volume of The Works of the Late Right Honorable Henry St. John, Lord Viscount Bolingbroke, 5 vols. (Dublin: Printed by P. Byrne: 1793). <Link to Google Books>
Reading also in the 1967 reprint of The Works of Lord Bolingbroke, 4 vols. (London: Henry G. Bohn, 1844).