"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?"

The poor youth's hair stood up straighter than ever, as though acted
upon by some magnetic force.