Nicene and Post-Nicene Fathers, Vol. II:
City of God: Chapter 22

Chapter 22.—Concerning Neptune, and Salacia and Venilia.

Now Neptune had Salacia to wife, who they say is the nether waters of the sea.  Wherefore was Venilia also joined to him?  Was it not simply through the lust of the soul desiring a greater number of demons to whom to prostitute itself, and not because this goddess was necessary to the perfection of their sacred rites?  But let the interpretation of this illustrious theology be brought forward to restrain us from this censuring by rendering a satisfactory reason.  Venilia, says this theology, is the wave which comes to the shore, Salacia the wave which returns into the sea.  Why, then, are there two goddesses, when it is one wave which comes and returns?  Certainly it is mad lust itself, which in its eagerness for many deities resembles the waves which break on the shore.  For though the water which goes is not different from that which returns, still the soul which goes and returns not is defiled by two demons, whom it has taken occasion by this false pretext to invite.  I ask thee, O Varro, and you who have read such works of learned men, and think ye have learned something great,—I ask you to interpret this, I do not say in a manner consistent with the eternal and unchangeable nature which alone is God, but only in a manner consistent with the doctrine concerning the soul of the world and its parts, which ye think to be the true gods.  It is a somewhat more tolerable thing that ye have made that part of the soul of the world which pervades the sea your god Neptune.  Is the wave, then, which comes to the shore and returns to the main, two parts of the world, or two parts of the soul of the world?  Who of you is so silly as to think so?  Why, then, have they made to you two goddesses?  The only reason seems to be, that your wise ancestors have provided, not that many gods should rule you, but that many of such demons as are delighted with those vanities and falsehoods should possess you.  But why has that Salacia, according to this interpretation, lost the lower part of the sea, seeing that she was represented as subject to her husband?  For in saying that she is the receding wave, ye have put her on the surface.  Was she enraged at her husband for taking Venilia as a concubine, and thus drove him from the upper part of the sea?