Quick Description
Now, the quick answer is that the Hexapla was Origen's (ca. 185-254) six-columned synopsis containing the following versions of the Hebrew Bible/Old Testament: (1) the Hebrew text in Hebrew letters, (2) the Hebrew text in Greek letters, i.e., in Greek transliteration, (3) the Greek version of Aquila, (4) the Greek version of Symmachus, (5) the Greek version of the Seventy, and (6) the Greek version of Theodotion. So far this description matches the early patristic descriptions of Eusebius and Epiphanius of Salamis (who also say that for some books like Psalms, Origen had a Fifth and a Sixth edition; read about them here). Eusebius says:Having collected all of these [Greek versions], he divided them into sections, and placed them opposite each other, with the indication (σημείωσις) itself of Hebrew [Ἑβραίων pl.] [versions?]. He thus left us the copies (ἀντίγραφον) of the so-called Hexapla, having arranged separately the edition (ἔκδοσις) of Aquila and Symmachus and Theodotion with the edition of the Seventy in the Tetrapla (Hist. eccl. 6.16.4; ANFP [adapted]).The term σημείωσις "indication, inference from a sign" is an interesting way to describe a "text," but perhaps this term indicates the Hebrew versions in Columns 1 and 2; that is, the Hebrew and its inference, meaning its sense or meaning in transliteration. Since he calls this work "the Hexapla" and there are four Greek versions, he must envision the very "inference" of Hebrews as two texts. Now, there are two problems we should address.
Two Major Problems
(1) Was there a Hebrew text in Column 1? Some modern scholars have questioned whether there was a Hebrew column (P. Nautin), since our scarce manuscript remains of the synopsis do not preserve the Hebrew in Hebrew letters (remains of Column 2 can be clearly seen in the very important evidence presented in an earlier post by Dirk Jongkind on Rahlfs 86 and elsewhere). In an important paper on the palimpsests of the Cairo Geniza (Rahlfs 2005) and of the Milan Codex (Rahlfs 1098), R. G. Jenkins has shown that the remains of the synopsis in 2005 are best interpreted as a trimmed down leaf (NEW) of an originally larger leaf (OLD) capable of containing the six columns of the Hexapla. But in any case, the patristic description of the Hexapla in six columns, two Hebrew and four Greek, is fairly straightforward.(2) Did the Fifth Column contain Critical Signs? In his Matthew Commentary (XV, 14; written post 244), Origen comments:
For when there are doubts about the Seventy on account of the disagreement of the copies, we, by making a judgment from the rest of the Versions, keep the agreement with these (= the rest of the Versions), and we use an obelus for some [Greek readings] <because> they are not in the Hebrew (not daring to remove any of these), and we place other readings under asterisks, in order that it might be clear that we have added the [readings] not present with the Seventy from the rest of the Versions to keep harmony with the Hebrew.This text has been scrutinized but what is clear is that Origen used an asterisk (※) to mark text not in the Seventy but in the Hebrew and an obelus (÷; or sometimes described as a lance or spear) to mark text in the Seventy but not in the Hebrew. An oft missed observation on this passage is that Origen nowhere calls his work "the Hexapla" here or elsewhere, yet this passage is often assumed to be a description of the Fifth column of the Hexapla. A better way forward could be to assume (which some scholars have done) that the differences between Versions would have been clear enough to the reader in the columnar synopsis and there would have been no need for these signs in the Hexapla. That would mean that in the Matthew Commentary Origen described another text of his in which he used the signs (what Eusebius called the Tetrapla, perhaps?). I have added to the speculation about what that text was here. But far more work needs to be done to answer this question satisfactorily.