Back in April, I had a Facebook conversation with an ex-Mormon who is now some sort of protestant Christian (probably of an Evangelical variety). In this conversation, this individual confessed that when she was a Mormon and prayed about the Book of Mormon, she did feel something. She said, “I don't deny the good feeling. It was there. I just don't think it was God anymore. I think it was a false spirit. Do you believe this is possible?”
The following is my response to her question. She never responded back to me, so I do not know what her thoughts were concerning this answer. So, I just thought I would share it here thinking others may find it helpful in dealing with the same criticism, or that perhaps I may get some kind of response or feedback from someone who disagrees.
Keep in mind that this response was written to a practicing Christian (as opposed to a non-Christian critic), so the truth of the Bible is assumed in my reasoning of why I feel that it is the Spirit of God that bears witness of the Book of Mormon. Also, I have slightly edited it to weed out mistakes in grammar and punctuation, etc. which I missed when I first wrote it.
As far as if I think it’s possible that a false spirit is what answers the prayers of people who seek to know that truth of the Book of Mormon, or the LDS Church, I would have to answer no. Certainly false spirits exist, and I suppose it is theoretically possible, but based on my experience, I must dismiss this notion. I have several reasons for this. I'll assume you won't mind if I delve into the scriptures to explain my reasoning:
1. Good Things Come From God: I'm sure you are familiar with the teaching in the Book of Mormon that “all things which are good cometh of God; and that which is evil cometh of the devil” and “that which is of God inviteth and enticeth to do good continually” (Moro. 7:12-13, also see verses 11-17). This is consistent with the principle that the Savior taught by analogy with the fig trees which bring forth good and bad fruit (see Matt. 7:16-18), namely that good comes from that which is good and of God, and bad evil things come from things that are corrupt and evil. The spiritual feelings I have experienced have been good feelings. They have led me to good things. Following the teachings of the Book of Mormon (and other scripture) and the LDS Church has resulted in more and more good in my life. Based in this simple principle, I must conclude that the good feelings are from God and not a false spirit.
2. Feelings Consistent with the Spirit of God: The Apostle Paul taught Timothy that “God hath not given us the spirit of fear; but of power, and of love, and of a sound mind.” (2 Tim 1:7) He likewise taught the Galatians that the fruits of the Spirit of God are (among other things) love, joy, peace, goodness, and faith (see Gal. 5:22-23). Jesus taught that the Holy Ghost was a comforter (see John 14:26), and that it would testify of truth (see John 16:13). Thus, the Holy Ghost (or Spirit of God) is a spirit of power, love, joy, peace, comfort, truth, goodness, faith and a sound mind. That description is consistent with the spiritual feelings I have experienced. They are likewise the feelings I feel coming from the Book of Mormon, and the LDS Church. In contrast, Paul mentioned a “spirit of fear” which is not of God. I have never felt fear from either the Book of Mormon or the LDS Church teachings. Paul also spoke to Timothy of “seducing spirits” which taught “doctrines of devils” (1 Tim 4:1). The things he says are taught by these spirits are (a) “speaking lies in hypocrisy” (b) “forbidding to marry” (c) and “abstaining from meats” (1 Tim. 4:2-3). I don't find any of these things coming from the spirit which I have felt. In fact, I find just the opposite. I got married back in August. I felt the Spirit confirm and encourage this decision, rather than “forbid to marry.” I have also felt this same Spirit encourage me to be honest at times when I have been tempted to “speak lies.” These are just some quick examples from my own experience.
3. The Holy Ghost Testifies of Christ: Probably the most important test (at least in my opinion) given in the scriptures on how to determine the Spirit of God from false spirits is given by the Apostle John. He taught that to “try the spirits” we feel, we need to know if the spirit we feel testifies of Jesus Christ. If it does, then that spirit is God, but if not, then that is not God’s spirit (see 1 John 4:1-3). The Apostle Paul also taught that no one can honestly testify of Jesus Christ except by the Holy Ghost (see 1 Cor. 12:3). Jesus likewise taught that the Spirit testifies of Him (see John 15:26). Thus we have an important way to test the spirit which we feel. Does it testify of Jesus Christ? Because the Book of Mormon itself testifies of Jesus Christ, any spirit which testifies of the Book of Mormon inherently testifies of Christ (the same goes for Joseph Smith and the LDS Church). However, I do feel that it is important that you seek a testimony of Jesus Christ independent of any other testimony. The spirit felt testifying of Jesus Christ is the Spirit of God. I have felt the Spirit of God testify to me of Jesus Christ as my Savior, Redeemer, Lord and God. That same spirit has testified to me of the Book of Mormon, Joseph Smith, and the LDS Church. It is also the same spirit that has testified to me of the truth of the Bible.
Sorry that was really long. But that lays out my experience and reasoning on the matter. If the spirit I felt testify of the Book of Mormon and the LDS Church was a false spirit, then I must reject the Bible, and Jesus Christ Himself, because the same spirit has given me my testimony of all those things.
This is just my experience. I can't speak for you or anyone else, but I can say I have a hard time believing that the Spirit of God and a false spirit would testify of the same things.