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Dominus, a word so repugnant to liberty (as it generally implied the authority over slaves), was not adopted by the first emperors, nor afterwards by those who preferred to rule rather through the affection than the fears of their subjects; and at any rate they did not approve of it. Augustus declined it, and, to use the words of Tertullian, 'Though the founder of the empire, he would not allow himself to be styled Dominus; and, indeed, it is an appellation applicable only to the deity.' And further on, he adds, 'How can he, who is the father of his country, be also its Lord (Dominus)?' Even Tiberius also avoided it, openly declaring, 'that he was lord (dominus) over the slaves, general (imperator) of the soldiers, and sovereign (princeps) of the rest of his people:'-- nay, according to Suetonius, he went so far as to address the Senators by that very invidious title, which in his own case he refused to accept, saying, 'I have never esteemed you, and still do so, as my good, and just, and kind Lords (Dominos).'--Caligula was the first whose arrogant ears could endure the appellation dominus, and his example was followed by that rival of his vices, Domitian.--Victor, whilst satirizing the character of Diocletian, remarks, 'He was the fist, after Caligula and Domitian, who allowed himself to be called openly Dominus.' This was the less remarkable in Domitian, as he wished to be called not only dominus but deus, of both which appellations Martial furnishes many instances. By degrees, however, the offensiveness of this title became softened fom use and familiarity, so that by the time of Ti. Claudius it was regarded merely as a term of courtesy.--Seneca says, 'You have called him friend, just in the same way as we call all candidates good men, or as we salute persons whom we meet, should we not remember their names as Domini.'--It is not surprising that Trajan himself should have permitted Pliny to address him constantly in his epistles as Dominus.
Antoninus Pius was the first to whom the title of Dominus was applied on coins; but it was Greece and Asia--conquered Greece and captured Asia--which furnished the instances, as usual, of extreme adulation. The word kyrios (Lord) is found on a coin of Antioch ad Hippum, in Decapolis--thus AUTOKR. KUR. ANTWNEINO c. Shortly afterwards, on coins of M. Aurelius and his family, struck in Mesopotamia, a similar use is made of the word kyrios. On coins of the colony of Antioch, in Pisidia, with the heads of Caracalla and Geta, we read VICT. DD. NN. And on a coin of Gordianus Pius, minted in the same colony, applears VICTORIA DOMINI.
The foregoing examples, however, belong only to the foregn coinage. It was the Emperor Aurelian who first introduced the title Dominus upon coins of Roman die, when he allowed the following inscription to appear:--DEO ET DOMINO NATO (on others (NOSTRO) AVRELIANO AVG. (see p. 319 of this dictionary). Next to the above, in point of time, Diocletianus and Maximinus, received the distinction of D.N. but not until their abdication of the empire (A.D. 305). Afterwards, it was conferred more frequently on the Caesars than on the Emprors, though for what reason is uncertain. Lastly, from the times of the sons of Constantine the Great, it became a common prenomen, that of IMPerator being gradually abolished. And at length it was rendered so much matter of course, that if any one in the reign of Justinian, had used the word Imperator instead of Dominus, and of Augusta instead of Domina, he would have been considered guilty of an insult, or at least of great ignorance.--See Doct. Num. Vet. viii. p. 364-5-6.