Front Page Titles (by Subject) FACULTY. - The Works of Voltaire, Vol. IV (Philosophical Dictionary Part 2)
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FACULTY. - Voltaire, The Works of Voltaire, Vol. IV (Philosophical Dictionary Part 2) 
The Works of Voltaire. A Contemporary Version. A Critique and Biography by John Morley, notes by Tobias Smollett, trans. William F. Fleming (New York: E.R. DuMont, 1901). In 21 vols. Vol. IV.
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All the powers of matter and mind are faculties; and, what is still worse, faculties of which we know nothing, perfectly occult qualities; to begin with motion, of which no one has discovered the origin.
When the president of the faculty of medicine in the “Malade Imaginaire,” asks Thomas Diafoirus: “Quare opium facit dormire?”—Why does opium cause sleep? Thomas very pertinently replies, “Quia est in eo virtus dormitiva quæ facit sopire.”—Because it possesses a dormitive power producing sleep. The greatest philosophers cannot speak more to the purpose.
The honest chevalier de Jaucourt acknowledges, under the article on “Sleep,” that it is impossible to go beyond conjecture with respect to the cause of it. Another Thomas, and in much higher reverence than his bachelor namesake in the comedy, has, in fact, made no other reply to all the questions which are started throughout his immense volumes.
It is said, under the article on “Faculty,” in the grand “Encyclopædia,” “that the vital faculty once established in the intelligent principle by which we are animated, it may be easily conceived that the faculty, stimulated by the expressions which the vital sensorium transmits to part of the common sensorium, determines the alternate influx of the nervous fluid into the fibres which move the vital organs in order to produce the alternate contradiction of those organs.”
This amounts precisely to the answer of the young physician Thomas: “Quia est in eo virtus alterniva quæ facit alternare.” And Thomas Diafoirus has at least the merit of being shortest.
The faculty of moving the foot when we wish to do so, of recalling to mind past events, or of exercising our five senses; in short, any and all of our faculties will admit of no further or better explanation than that of Diafoirus.
But consider thought! say those who understand the whole secret. Thought, which distinguishes man from all animals besides: “Sanctius his animal, mentisque capacius altæ.” (Ovid’s Metamorph. i. 76.)—More holy man, of more exalted mind!
As holy as you like; it is on this subject, that of thought or mind, that Diafoirus is more triumphant than ever. All would reply in accordance with him: “Quia est in eo virtus pensativa quæ facit pensare.” No one will ever develop the mysterious process by which he thinks.
The case we are considering then might be extended to everything in nature. I know not whether there may not be found in this profound and unfathomable gulf of mystery an evidence of the existence of a Supreme Being. There is a secret in the originating or conservatory principles of all beings, from a pebble on the seashore to Saturn’s Ring and the Milky Way. But how can there be a secret which no one knows? It would seem that some being must exist who can develop all.
Some learned men, with a view to enlighten our ignorance, tell us that we must form systems; that we shall at last find the secret out. But we have so long sought without obtaining any explanation that disgust against further search has very naturally succeeded. That, say they, is the mere indolence of philosophy; no, it is the rational repose of men who have exerted themselves and run an active race in vain. And after all, it must be admitted that indolent philosophy is far preferable to turbulent divinity and metaphysical delusion.