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 qu? 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 “Encyclop?dia,” “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 qu? 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 recallin............