One of the first differences which are obvious, in comparing the Christian with the heathen mortuary inscriptions, is the introduction in the former of some new words, expressive of the new ideas that prevailed among them.  Thus, in place of the old formula which had been in most common use upon gravestones, D.M., or, in Greek, [Greek:  Th.K.], standing for Dis Manibus, or [Greek:  Theois karachthoniois], a dedication of the stone to the gods of death, we find constantly the words In pace.  The exact meaning of these words varies on different inscriptions, but their general significance is simple and clear.  When standing alone, they seem to mean that the dead rests in the peace of God; sometimes they are preceded by Requiescat, “May he rest in peace”; sometimes there is the affirmation, Dormit in pace, “He sleeps in peace”; sometimes a person is said recessisse in pace, “to have departed in peace.”  Still other forms are found, as, for instance, Vivas in pace, “Live in peace,” or Suscipiatur in pace, “May he be received into peace,”—­all being only variations of the expression of the Psalmist’s trust, “I will lay me down in peace and sleep, for thou, Lord, only makest me dwell in safety.”  It is a curious fact, however, that on some of the Christian tablets the same letters which were used by the heathens have been found.  One inscription exists beginning with the words Dis Manibus, and ending with the words in pace.  But there is no need of finding a difficulty in this fact, or of seeking far for an explanation of it.  As we have before remarked, in speaking of works of Art, the presence of some heathen imagery and ideas in the multitude of the paintings and inscriptions in the catacombs is not so strange as the comparatively entire absence of them.  Many professing Christians must have had during the early ages but an imperfect conception of the truth, and can have separated themselves only partially from their previous opinions, and from the conceptions that prevailed around them in the world.  To some the letters of the heathen gravestones, and the words which they stood for, probably appeared little more than a form expressive of the fact of death, and, with the imperfect understanding natural to uneducated minds, they used them with little thought of their absolute significance.[1]

[Footnote 1:  It is probable that most of the gravestones upon which this heathen formula is found are not of an earlier date than the middle of the fourth century.  At this time Christianity became the formal religion of many who were still heathen in character and thought, and cared little about the expression of a faith which they had adopted more from the influence of external motives than from principle or conviction.]