By laying all these circumstances together, and comparing them, we may, I think, not only find out wherein the mistake consisted, but likewise explain the grounds from whence the mistake arose. And this clue may lead us to the detection of other fallacies, and those of greater consequence. We may hence learn the reason, why so many Deities were styled Πετραιοι, Petræi. We read of[883] Μιθρας, ὁ θεος εκ πετρας, _Mithras, the Deity out of the rock_; whose temple of old was really a rock or cavern. The same worship seems to have prevailed, in some degree, in the west; as we may judge from an antient inscription at Milan, which was dedicated[884] Herculi in Petrâ. But all Deities were not so worshipped: and the very name Petra was no other than the sacred term Petora, given to a cavern, as being esteemed in the first ages an oracular temple. And some reverence to places of this sort was kept up a long time. We may from hence understand the reason of the prohibition given to some of the early proselytes to Christianity, that they should no more[885] ad petras vota reddere: and by the same light we may possibly explain that passage in Homer, where he speaks of persons entering into compacts under oaks, and rocks, as places of[886] security. The oak was sacred to Zeus, and called Sar-On: and Petra in its original sense being a temple, must be looked upon as an asylum. But this term was not confined to a rock or cavern: every oracular temple was styled Petra, and Petora. Hence it proceeded that so many Gods were called Θεοι Πετραιοι, and Πατρῳσι. Pindar speaks of Poseidon Petraios;[887] Παι Ποσειδωνος Πετραιου: under which title Neptune was worshipped by the Thessalians: but the latter was the more common title. We meet in Pausanias with Apollo Patroüs, and with [888]Ζευς Μειλιχιος, and Αρτεμις Πατρῳα; also [889]Bacchus Πατρῳος, Zeus Patroüs, and Vesta Patroa, together with other instances. The Greeks, whenever they met with this term, even in regions the most remote, always gave it an interpretation according to their own preconceptions; and explained θεοι Πατρῳοι, the oracular Deities, by Dii Patrii, or the Gods of the country. Thus, in the Palmyrene inscription, two Syrian Deities are characterized by this title. [890]ΑΓΛΙΒΩΛΩ ΚΑΙ ΜΑΛΑΧΒΗΛΩ ΠΑΤΡΩΟΙΣ ΘΕΟΙΣ.