To this it was answered that, as that is said to be most sweet which is perfectly sweet, and to be most white which is perfectly white (I mean here by perfectly that which hath nothing of a contrary quality mixed with it), so that ought to be called perfectly humid whereof never a part is dry; and this is proper to oil.
For first of all, its smoothness shows the evenness of its parts; for touch it where you please, it is all alike.

Besides, you may see your face in it as perfectly as in a mirror; for there is nothing rough in it to hinder the reflection, but by reason of its humidity it reflects to the eye the least particle of light from every portion.

As, on the contrary, milk, of all other liquids, does not return our images, because it hath too many terrene and gross parts mixed with it; again, oil of all other liquids makes the least noise when moved, for it is perfectly humid.

When other liquids are moved or poured out, their hard and grosser parts fall and dash one against another, and so make a noise by reason of their roughness.

Moreover, oil only is pure and unmixed; for it is of all other liquids most compact, nor has it any empty spaces and pores between the dry and earthy parts to receive what chances to fall upon it.