Ambrose of Milan : The third river is the Tigris, which flows by the Assyrian land. To this river the deceiver Israel was dragged as a prisoner. This river is the swiftest of all rivers. The Assyrians dwell by it, guarding its course—for this is the meaning of its name. Hence those who by their fortitude hold in check the guileful vices of the body and direct themselves to higher things are thought to have something in common with this river. For that same reason fortitude emanates from that source in paradise. Fortitude in its rapid course tosses aside everything standing in its path and like this river is not hindered by any material obstacle. — On Paradise Ambrose of Milan : The fourth river is the Euphrates, which means in Latin "fecundity and abundance of fruits." It presents a symbol of justice, the nourishment of every soul. No virtue produces more abundant benefits than equity or justice, which is more concerned with others than with itself, neglecting its own advantages and preferring the common good. Many derive Euphrates from the Greek apo tou euphrainesthai, that is, from a "feeling of gladness," because the human race rejoices in nothing more than it does in justice and equity. The question as to why, although the location itself of other rivers is reported, we have no description of the regions through which the river Euphrates flows calls for an answer. The waters of this river are considered to have a vital quality that fosters growth and increase. Wherefore the wise men among the Hebrews and the Assyrians called this river Auxen ["increase"] in contradistinction to the water of other rivers. The opposition has been well established between wisdom and malice, fortitude and irascibility, temperance, and other vices. Justice, on the other hand, is the most important as it represents the concord of all the other virtues. Hence it is not known from the places from which it flows, that is to say, it is not known in part. Justice is not divisible into parts. It is, as it were, the mother of all virtues. In these four rivers are symbolized therefore the four principal virtues. — On Paradise Ephrem the Syrian : Now these four rivers are as follows: the Pishon, that is, the Danube; the Gihon, that is, the Nile; the Tigris and the Euphrates. In between these we live. Even though the regions from which these flow are known, this does not apply to the head of the source; for Paradise is situated on a great height, and the rivers are swallowed up under the surrounding sea, descending as it were down a tall water pipe; having passed through the ground beneath the sea and reached this earth, the earth then spouts forth with one of them in the West-the Danube, or Pishon-the Gihon in the South, and the Euphrates and Tigris in the North. Ephrem the Syrian : The four rivers, then, are these: the Pishon, which is the Danube; the Gihon, which is the Nile; and then the Tigris and the Euphrates, between which we dwell. Although the places from which they flow are known, the source of the spring is not known. Because paradise is set on a great height, the rivers are swallowed up again, and they go down to the sea as if through a tall water duct, and so they pass through the earth that is under the sea into this land. The earth then spits out each one of them: the Danube, which is the Pishon, in the west; the Gihon in the south; and the Euphrates and the Tigris in the north. — COMMENTARY ON Genesis 2.6