Why is the Son of God called the Eternal Father in the book of Alma? I happened across the following verses in the book of Alma:


  Now Zeezrom saith again unto him: Is the Son of God the very Eternal Father? And Amulek said unto him: Yea, he is the very Eternal Father of heaven and of earth, and all things which in them are; he is the beginning and the end, the first and the last;  Alma 11:38-39


This seems to differ from the Articles of Faith of the LDS Church, where it states the following:


  We believe in God, the Eternal Father, and in His Son, Jesus Christ, and in the Holy Ghost.  Articles of Faith 1:1


So, what did Amulek mean here?  Was he in error or did he have incomplete knowledge at the time?
He was using the words of the prophet Abinadi from years earlier in Mosiah 15:

1 And now Abinadi said unto them: I would that ye should understand that God himself shall come down among the children of men, and shall redeem his people.
2 And because he dwelleth in flesh he shall be called the Son of God, and having subjected the flesh to the will of the Father, being the Father and the Son—
3 The Father, because he was conceived by the power of God; and the Son, because of the flesh; thus becoming the Father and Son—
4 And they are one God, yea, the very Eternal Father of heaven and of earth.
5 And thus the flesh becoming subject to the Spirit, or the Son to the Father, being one God, suffereth temptation, and yieldeth not to the temptation, but suffereth himself to be mocked, and scourged, and cast out, and disowned by his people.

Jesus Christ is &quot;the very Eternal Father of heaven and of earth&quot; because He created them (Hebrews 1:1-2). He is the Father of physical creation. (Incidentally, but out of the scope of this answer, there is great and interesting symbolism in Abinadi using the term &quot;one God&quot; to describe them.)
Though Book of Mormon prophets sometimes call Christ the Eternal Father, it's less commonly done today, perhaps because the distinction between Father and Son is important in LDS theology, so as to stand out from the diverse ways the Godhead/Trinity is interpreted across so many Christian denominations.