This exchange is an apparent duplication of the exchange in verses 2 and 3 of this chapter, where the Spirit also asks what Nephi desires. In this case, however, the repetition is either a stylistic technique used by Nephi to emphasize the delving into the dream, or was actually used by the Spirit to urge Nephi to plumb the depths of his real desires.
In any case, the effect is that Nephi progresses from his original simplistic desire to see what his father saw, to the real reason for his quest, which was understanding.
Identifying the "Spirit of the Lord" There are two opinions about the identity of the Spirit of the Lord who introduces the vision to Nephi. One opinion is that it is the Spirit person of Christ, and the other is that it was the spirit person of the Holy Ghost.
Bruce R. McConkie expressed the first view:
"To gain a sound gospel understanding, the truth seeker must determine in each scriptural passage what is meant by such titles as Spirit, Holy Spirit, Spirit of the Lord, Spirit of God, Spirit of truth. In many instances this is not difficult; in some cases, however, abbreviated scriptural accounts leave so much room for doubt that nothing short of direct revelation can identify precisely what is meant. We know, for instance, that the Spirit personage who appeared to the Brother of Jared was the Spirit Christ, for he so identified himself. (Ether 3.) But when we read the account of the appearance of "the Spirit of the Lord" to Nephi (1 Ne. 11), we are left to our own interpretive powers to determine whether the messenger is the Spirit Christ or the Holy Ghost. Presumptively it is the Spirit Christ ministering to Nephi much as he did to the Brother of Jared, for such is in keeping with the principle of advocacy, intercession, and mediation, the principle that all personal appearances of Deity to man since the fall of Adam, excepting appearances of the Father and the Son together, have been appearances of Christ."1 (Mormon Doctrine, p.752 SPIRIT OF THE LORD)
However, in other writings, Bruce R. McConkie understands the title Spirit of the Lord to mean the Holy Ghost (see The Mortal Messiah, Vol.1, p.413 - p.414). While the title is most often associated with the Spirit of the Lord, Elder McConkie apparently believed that the circumstances of Nephi's vision were sufficiently exceptional to hold for the interpretation that the Spirit of the Lord was, in that case, the spirit person of Jesus Christ before his birth.
The opposite interpretation was espoused by B.H. Roberts and James E.Talmage, among others:
"That the Holy Ghost is capable of manifesting himself in the true form and figure of God, after which image man is shaped, is indicated by the wonderful interview between the Spirit and Nephi, in which he revealed himself to the Prophet, questioned him concerning his desires and belief, instructed him in the things of God, speaking face to face with the man. 'I spake unto him,' says Nephi, 'as a man speaketh; for I beheld that he was in form of a man, yet nevertheless I knew that it was the Spirit of the Lord; and he spake unto me as a man speaketh to another.'" B.H. Roberts, (The Seventy's Course in Theology, Fifth Year, p.60)
"That the Spirit of the Lord is capable of manifesting Himself in the form and figure of man, is indicated by the wonderful interview between the Spirit and Nephi, in which He revealed Himself to the prophet, questioned him concerning his desires and belief, instructed him in the things of God, speaking face to face with the man. "I spake unto him," says Nephi,"as a man speaketh; for I beheld that he was in the form of a man; yet nevertheless, I knew that it was the Spirit of the Lord; and he spake unto me as a man speaketh with another." James E. Talmage, (Articles of Faith, Ch.8, p.159 - p.160)
The virtually exact correspondence of these two citations indicates that either the one is citing the other, or that both are citing another document. I am unaware of the original source which both of these brethren would be quoting.
To take a side in the issue, I suggest that the preponderance of "Spirit of the Lord" as a title for the Holy Ghost lends the greatest strength to that identification.