Nicene and Post-Nicene Fathers, Vol. II:
City of God: Chapter 8

Chapter 8.—For What Reason the Worshippers of Janus Have Made His Image with Two Faces, When They Would Sometimes Have It Be Seen with Four.

But now let the interpretation of the two-faced image be produced.  For they say that it has two faces, one before and one behind, because our gaping mouths seem to resemble the world:  whence the Greeks call the palate οὐρανός, and some Latin poets, 266 he says, have called the heavens palatum [the palate]; and from the gaping mouth, they say, there is a way out in the direction of the teeth, and a way in in the direction of the gullet.  See what the world has been brought to on account of a Greek or a poetical word for our palate!  Let this god be worshipped only on account of saliva, which has two open doorways under the heavens of the palate,—one through which part of it may be spitten out, the other through which part of it may be swallowed down.  Besides, what is more absurd than not to find in the world itself two doorways opposite to each other, through which it may either receive anything into itself, or cast it out from itself; and to seek of our throat and gullet, to which the world has no resemblance, to make up an image of the world in Janus, because the world is said to resemble the palate, to which Janus bears no likeness?  But when they make him four-faced, and call him double Janus, they interpret this as having reference to the four quarters of the world, as though the world looked out on anything, like Janus through his four faces.  Again, if Janus is the world, and the world consists of four quarters, then the image of the two-faced Janus is false.  Or if it is true, because the whole world is sometimes understood by the expression east and west, will any one call the world double when north and south also are mentioned, as they call Janus double when he has four faces?  They have no way at all of interpreting, in relation to the world, four doorways by which to go in and to come out as they did in the case of the two-faced Janus, where they found, at any rate in the human mouth, something which answered to what they said about him; unless perhaps Neptune come to their aid, and hand them a fish, which, besides the mouth and gullet, has also the openings of the gills, one on each side.  Nevertheless, with all the doors, no soul escapes this vanity but that one which hears the truth saying, “I am the door.” 267

Footnotes

Ennius, in Cicero, De Nat. Deor. ii. 18.

John 10.9.