"In general, the violent Sensations of Pain or Uneasiness which accompany Hunger, Thirst, and the other private Appetites, or too great Fatigue of Mind as well as of Body, prevent the Individual from running to great Excesses in the Exercise of the higher Functions of the Mind, as too intense Thought in the Search of Truth, violent Application to Business of any kind, and different Degrees of Romantic Heroism."
— Fordyce, David (bap. 1711, d. 1751)
See The Elements of Moral Philosophy. In Three Books. 1. Of Man, and His Connexions. Of Duty or Moral Obligation. - Various Hypotheses Final Causes of Our Moral Faculties of Perception and Affection. 2. The Principal Distinction of Duty or Virtue. Man's Duties to Himself. - To Society. - To God. 3. Of Practical Ethics, or the Culture of the Mind. Motives to Virtue from Personal Happiness. - From the Being and Providence of God. - From the Immortality of the Soul. The Result, or Conclusion. By the Late Rev. Mr. David Fordyce. Professor of Moral Philosophy, and Author of the Art of Preaching, Inscribed to His Grace the Archbishop of Canterbury. (London: Printed for R. and J. Dodsley in Pallmall, 1754). <Link to ESTC>
See also The Preceptor: Containing a General Course of Education. Wherein the First Principles of Polite Learning Are Laid Down in a Way Most Suitable for Trying the Genius, and Advancing the Instruction of Youth. In Twelve Parts. Viz. I. On Reading, Speaking, and Writing Letters. II. On Geometry. III. On Geography and Astronomy. IV. On Chronology and History. V. On Rhetoric and Poetry. VI. On Drawing. VII. On Logic. VIII. On Natural History. IX. On Ethics, or Morality. X. On Trade and Commerce. XI. On Laws and Government. XII. On Human Life and Manners. Illustrated With Maps and Useful Cuts. 2 vols. (London: Printed for R. Dodsley, at Tully's-Head in Pall-Mall, 1748). <Link to ESTC> [The Preceptor was reprinted 1748, 1749, 1754, 1758, 1761-65, 1763, 1765, 1769, 1775, 1783, 1786, and 1793.]
Reading and searching The Elements of Moral Philosophy, in Three Books with A Brief Account of the Nature, Progress and Origin of Philosophy, ed. Thomas Kennedy (Indianapolis: Liberty Fund, 2003). [The Liberty Fund text is based on the 1754 edition.] <Link to OLL>