“The name of mirror is applied to all polished surfaces intended to produce by the reflection of light the images of the objects placed before said surfaces.  From the substances that form these surfaces, they are divided into metallic mirrors and glass mirrors—­”

“Stop, stop, stop!” interrupted the professor.  “Heavens, what a rattle!  We are at the point where the mirrors are divided into metallic and glass, eh?  Now if I should present to you a block of wood, a piece of kamagon for instance, well polished and varnished, or a slab of black marble well burnished, or a square of jet, which would reflect the images of objects placed before them, how would you classify those mirrors?”

Whether he did not know what to answer or did not understand the question, the student tried to get out of the difficulty by demonstrating that he knew the lesson, so he rushed on like a torrent.

“The first are composed of brass or an alloy of different metals and the second of a sheet of glass, with its two sides well polished, one of which has an amalgam of tin adhering to it.”

“Tut, tut, tut!  That’s not it!  I say to you ‘Dominus vobiscum,’ and you answer me with ‘Requiescat in pace!’ "

The worthy professor then repeated the question in the vernacular of the markets, interspersed with cosas and abas at every moment.

The poor youth did not know how to get out of the quandary:  he doubted whether to include the kamagon with the metals, or the marble with glasses, and leave the jet as a neutral substance, until Juanito Pelaez maliciously prompted him: 

“The mirror of kamagon among the wooden mirrors.”

The incautious youth repeated this aloud and half the class was convulsed with laughter.

“A good sample of wood you are yourself!” exclaimed the professor, laughing in spite of himself.  “Let’s see from what you would define a mirror—­from a surface per se, in quantum est superficies, or from a substance that forms the surface, or from the substance upon which the surface rests, the raw material, modified by the attribute ‘surface,’ since it is clear that, surface being an accidental property of bodies, it cannot exist without substance.  Let’s see now—­what do you say?”

“I?  Nothing!” the wretched boy was about to reply, for he did not understand what it was all about, confused as he was by so many surfaces and so many accidents that smote cruelly on his ears, but a sense of shame restrained him.  Filled with anguish and breaking into a cold perspiration, he began to repeat between his teeth:  “The name of mirror is applied to all polished surfaces—­”

“Ergo, per te, the mirror is the surface,” angled the professor.  “Well, then, clear up this difficulty.  If the surface is the mirror, it must be of no consequence to the ‘essence’ of the mirror what may be found behind this surface, since what is behind it does not affect the ‘essence’ that is before it, id est, the surface, quae super faciem est, quia vocatur superficies, facies ea quae supra videtur.  Do you admit that or do you not admit it?”