The book of Joel admirably illustrates the intimate connection which subsisted for the prophetic mind between the sorrows and disasters of the present and the coming day of Jehovah: the one is the immediate harbinger of the other. In an unusually devastating plague of locusts, which, like an army of the Lord,[1] has stripped the land bare and brought misery alike upon city and country, man and beast -- "for the beasts of the field look up sighing unto Thee," i.20 -- the prophet sees the forerunner of such an impending day of Jehovah, bids the priests summon a solemn assembly, and calls upon the people to fast and mourn and turn in penitence to God. Their penitence is met by the divine pity and rewarded by the promise not only of material restoration but of an outpouring of the spirit upon all Judah,[2] which is to be accompanied by marvellous signs in the natural world. The restoration of Judah has as its correlative the destruction of Judah's enemies, who are represented as gathered together in the valley of Jehoshaphat -- i.e. the valley where "Jehovah judges" -- and there the divine judgment is to be executed upon them.
[Footnote 1: Some regard the locusts as an allegorical designation for an invading army. But without reason: in ii.7 they are compared to warriors, and the effect of their devastations is described in terms inapplicable to an army.]
[Footnote 2: The sequel, in which the nations are the objects of divine wrath, shows that the "all flesh," ii.28, must be confined to Judah.]

The theological value of the book of Joel lies chiefly in its clear contribution to the conception of the day of Jehovah. As Marti says, "The book does not present one side of the picture only, but combines all the chief traits of the eschatological hope in an instructive compendium" -- the effusion of the spirit, the salvation of Jerusalem, the judgment of the heathen, the fruitfulness of the land, the permanent abode of Jehovah upon Zion. These features of the Messianic hope are, in the main, characteristic of post-exilic prophecy; and now, with very great unanimity, the book is assigned, in spite of its position near the beginning of the minor prophets, to post-exilic times.

A variety of considerations appears to support this date. Judah is the exclusive object of interest. Israel has no independent existence, and, where the name is mentioned, it is synonymous with Judah, ii.27, iii.2, 16. Further, the people are scattered among the nations, iii.2, and strangers are not to pass through the "holy" Jerusalem any more, iii.17. The exile and the destruction of Jerusalem by Nebuchadrezzar in 586 B.C. appear therefore to be presupposed. But the temple has been rebuilt; there are numerous allusions to priests and to meal and drink offerings, i.9, 13, ii.14,17, and an assembly is summoned to "the house of Jehovah your God," i.14: the reference to the city wall, ii.9, would bring the date as late as Nehemiah in the fifth century. Other arguments, though more precarious, are not without weight, e.g., the ease and smoothness of the language, the allusion to the Greeks, in.6, the absence of any reference to the sin of Judah,[1] the apparent citations from or allusions to other prophetic books.[2] [Footnote 1: Though it may be implied in ii.12f ]
[Footnote 2: Obad. v.17, Jo. ii.32; Amos i.2, Jo. iii.16; Amos ix.13, Jo. iii.18; Ezek. xlvii.1ff., Jo. iii.18.]

The effect of this cumulative argument has been supposed to be overwhelming in favour of a post-exilic date. Recently, however, Baudissin, in a very careful discussion, has ably argued for at least the possibility of a pre-exilic date. Precisely in the manner of Joel, Amos iv.6-9 links together locusts and drought as already experienced calamities. Both alike complain of the Philistine and Phoenician slave-trade. The enemies -- Edom, Phoenicia, Philistia, iii.4, l9 -- fit the earlier period better than the Persian or Greek. In the ninth century, Judah was invaded by the Philistines and Arabians according to the Chronicler (2 Chron. xxi.16ff.), whose statements in such a matter there is no reason for doubting, and Jerusalem may then have suffered: in any case, we know that the treasures of temple and palace were plundered as early as Rehoboam's time (1 Kings xiv.25ff.), and this might be enough to satisfy the allusion in Joel iii.17. Again, if Joel is smooth, Amos is not much less so; and linguistic peculiarities that seem to be late might be due to dialect or personal idiosyncrasy. With regard to the argument from citations, it would be possible to maintain that Joel's simple and natural picture of the stream from the temple watering the acacia valley, iii.18, was not borrowed from, but rather suggested the more elaborate imagery of Ezekiel, xlvii. For these and other reasons Baudissin suggests with hesitation that a date slightly before Amos is by no means impossible.[1]
[Footnote 1: It is interesting to note that Vernes, Rothstein and Strack have independently reached the conclusion that chs. i., ii. have a different origin from iii., iv. In the former, the state still exists, and the calamity is a plague of locusts; in the latter, no account is taken of the locusts -- it is a time of national disaster. The reasons, however, are hardly adequate for denying the unity of the book.]

The question is much more than an academic one, for on the answer to it will depend our whole conception of the development of Hebrew prophecy. Sacerdotal interests, e.g., here receive a prominence in prophecy which we are accustomed to associate only with the period after the exile. Here again, the promises are for Judah, the threats for her enemies -- an attitude also characteristic of post-exilic prophecy: it is customary to deny to the pre-exilic prophets any word of promise or consolation to their own people. Obviously if the priest and the element of promise have already so assured a place in the earliest of the prophets, the ordinary view of the course of prophecy will have to be seriously modified. The lack of emphasis displayed by Joel on the ethical aspect of religion, which has been made to tell in favour of a late date, might tell equally well in favour of a very early one. Indeed, the book is either very early or very late; and, if early, it represents what we might call the pre-prophetic type of Israel's religion, and especially the non-moral aspirations of those who, in Amos's time, longed for the day of Jehovah, and did not know that for them it meant thick darkness, without a streak of light across it (Amos v.18). On the whole, however, the balance leans to a post-exilic date. The Jewish dispersion seems to be implied, iii.2. The strange visitation of locusts suggests to the prophet the mysterious army from the north, ii.20, which had haunted the pages of Ezekiel (xxxviii., xxxix.); and in this book, prophecy (i., ii.) merges into apocalyptic (iii., iv.).