Jacob has seen and heard something by the power of the Holy Ghost that proves all mankind would be lost without Christ.

In Jacob chapter 7 Jacob is telling Sherem that there must be a Christ.  He uses 2 proofs that there is a Christ.


First he proves there will be a Christ by the Scriptures.

  10 And I said unto him: Believest thou the scriptures? And he said, Yea.

  11 And I said unto him: Then ye do not understand them; for they truly testify of Christ. Behold, I say unto you that none of the prophets have written, nor prophesied, save they have spoken concerning this Christ.

Second he proves there will be a Christ by his own personal experiences.

  12 And this is not all—it has been made manifest unto me, for I have heard and seen; and it also has been made manifest unto me by the power of the Holy Ghost; wherefore, I know if there should be no atonement made all mankind must be lost.

Jacob must have seen and heard something that showed that all would be lost without Christ.  Perhaps he saw a world without Christ, or perhaps he saw the pre-existence.  We know he saw Christ.

2 Ne. 11: 2-3

  2 And now I, Nephi, write more of the words of Isaiah, for my soul delighteth in his words. For I will liken his words unto my people, and I will send them forth unto all my children, for he verily saw my Redeemer, even as I have seen him.

  3 And my brother, Jacob, also has seen him as I have seen him;

But just seeing Christ would not give you the knowledge that all mankind would be lost without him.  I wonder what he saw and heard.  The Lord definitely prepared Jacob to have this exact knowledge of Christ's atonement so that he could defend Christ to Sherem.  I wonder what we need to know to be able to defend Christ to those around us.