Joseph Smith's Book of Abraham contains a wealth of information about the patriarch Abraham that is not contained in the Bible, or indeed, in any documents that would have been available to Joseph Smith. Therefore, a simple test of Abraham's authenticity would be to peruse the Jewish Abraham texts and legends now available to find out if there are any parallels. (Hugh Nibley and Rabbi Nissim Wernick have used this approach in the past with great success, and some of their writings are linked at this site.)

The Apocalypse of Abraham is just such a text. Written in the first century A.D., the Apocalypse is most likely of Jewish origin, although there may have been some Christian interpolations in the text. This document has been preserved only in the Slavonic language, and was first published in 1863 - long after Joseph Smith was dead. It is an account of some events in the patriarch Abraham's life, including various revelations. Here's an excerpt from the text where Abraham sees the pre-existent host in a vision.

"And everything I had planned to be came into being: it was already pre-figured in this, for all the things and all the people you have seen stood before me before they were created. And I said, Mighty and Eternal Ruler, who then are the people in this picture on this side and on that? And he said to me, Those on the left side are the many peoples which have existed in the past, and after you are appointed, some for judgement and restoration, some for vengeance and perdition, until the end of the age. And those on the right side of the picture, they are the people set apart for me from the people with Azazil [Satan]. These are the people who are going to spring from you and will be called my people." [The Apocalypse of Abraham 22, in Sparks, ed., The Apocryphal Old Testament, p. 384.]

Compare that with the following passage from Joseph Smith's Book of Abraham:

"Now the Lord had shown unto me, Abraham, the intelligences that were organized before the world was; and among all these there were many of the noble and great ones; And God saw these souls that they were good, and he stood in the midst of them, and he said: These I will make my rulers; for he stood among those that were spirits, and he saw that they were good; and he said unto me: Abraham, thou art one of them; thou wast chosen before thou wast born." [Abraham 3:22-23]

Now consider the similarities between the two vision accounts: (1) Abraham (2) sees a vision of the pre-existent host (3) among whom were righteous spirits. And here the vision accounts part company, for while the Book of Abraham account focuses on the "noble and great" spirits who would become the "rulers" of God's people, the Apocalypse account focuses on all the righteous spirits who would become the seed of Abraham, father of the faithful.

Certainly the parallel is striking, and in combination with the many other possible links between the Book of Abraham and non-canonical Abraham texts, the evidence for its authenticity becomes almost undeniable.