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O Livro de Mórmon/Anacronismos/Cristianismo pré-cristão
Question: Is it an anachronism that the Book of Mormon teaches that Christians existed before Christ’s birth?
The word "Christ" is the Greek word for the Hebrew word "Messiah"
The word "Christ" is the Greek word for the Hebrew word "Messiah". It is no more anachronistic for pre-Christian era Book of Mormon peoples to believe in a coming Messiah/Christ than it was for Old Testament prophets to believe in a coming Messiah/Christ.
15 And those who did belong to the church were faithful; yea, all those who were true believers in Christ took upon them, gladly, the name of Christ, or Christians as they were called, because of their belief in Christ who should come.
The English word "Christian" is not the word that was originally on the Nephite record
It should be remembered that the Book of Mormon is a translation of an ancient Nephite text. The English word "Christian" is not the word that was originally on the Nephite record, but is the English word that Joseph Smith used when translating the original Nephite word. The word "Christian" simply means "Christ-believer" in common use and in the Book of Mormon. We don't know what the original Nephite word was for "Christian", but it signified something like "Christ-believer." The word "Christ" is a Greek word that means the same thing as the Hebrew word "Messiah." The concept of a future Messiah was taught in ancient Israel, and anyone who believed those prophecies would have been a "Messiah-believer". Therefore, all pre-Christian era Israelites who believed in the coming Messiah/Christ were Christians in this sense. This is the sense we find in the Book of Mormon.
Lehi and his family left the Old World carrying with them the plates of brass that they obtained from Laban (1 Nephi 4). These plates contained "the prophecies of the holy prophets, from the beginning, even down to the commencement of the reign of Zedekiah; and also many prophecies which have been spoken by the mouth of Jeremiah." (1 Nephi 5:13). Therefore, the Nephites knew about the ancient prophecies of the future Messiah/Christ. Furthermore, the Book of Mormon records many more prophecies by New World prophets of the coming Messiah/Christ. All those who believed these prophecies were "Messiah-believers" or, equivalently, "Christ-believers." The English word that Joseph Smith used to convey this meaning was "Christian."