The fourth kingdom, &c. Some understand this of the successors of Alexander, the kings of Syria and Egypt: others, of the Roman empire and its civil wars. (Challoner)

The former supposition seems best, though the latter is almost universally received, and will be explained hereafter. (Calmet)

The Roman empire did not immediately rise out of Alexander’s, and had no relation to the Jews, &c. (Grotius, L’Empereus.)

But it surely swallowed up all that he had left to his generals, and proved the greatest scourge to the Jewish nation; which has been ever since scattered, while the kingdom of Christ gains ground, and will flourish till that of Rome shall be no more. Antichrist will then appear to cast a cloud over, but not destroy it for three years and a half. It is the opinion of many Fathers, &c. that the Roman empire will subsist till that event take place; (see 2 Thessalonians ii. 3, 7.) and thus it may be said, that the fourth empire shall not be given to another people. For antichrist will not strive to exalt a particular nation, but to rule over all. Yet his dominion will be short, and will end in the general dissolution of nature; so that the Roman empire may be deemed to last for a long time, or even for ever. (ver. 44.) Those who adopt the former system, allow (Haydock) that the stone designates both the Roman empire and that of Christ; so that some parts of the prediction may refer to one and some to the other. The origin and progress of the Roman empire, might be a figure of the spiritual power of the Church. It is certain that the successors of Alexander owed their dominion to their valour, and established it by the slaughter of many great generals. The kings who followed Seleucus and Ptolemy were remarkable for a mixture of good and bad qualities. Their efforts to preserve their power by intermarriages, proved abortive. The prophet seems also to have had them in view, chap. vii. 7., and viii. 22. (Calmet)