“Take up the Bible, compare the religion of the Latter-day Saints with it, and see if it will stand the test.” -- Brigham Young, Journal of Discourses, Vol. 16, p. 46

My logic and evidence for why The Book of Mormon is not the word of God and why Joseph Smith is not a prophet:
 

• After Joseph Smith "translated" the Book of Lehi and wouldn't translate it again when it was hidden, he said instead, "I'm going to do a new translation, the Book of Nephi; it's the same story, but just told a little different." -- doesn't that sound a little odd to you? Think about it, it's the same general story, just from a slightly different perspective. I think he made it up. He knew in his mind the basic, general story that he wanted to "translate", but knew that with that opener to his book lost, he was in a big fix, so to weasel out he came up with the book of Nephi -- slightly different, but the same opener to his story. A sly slight of hand that amazingly a lot of people have fallen for.
 

• Yes, Joseph Smith could have made it up. Someone in an exmo yahoo group put it very well:
"I truly believe that J.R. Tolkien translated the Lord of the Rings. What a great book. Middle Earth must have existed. It is impossible to make that up."
-- Arnie Norse, arnie@lds.net
 

• Joseph Smith didn't have any gold plates when he translated! In 1879, Emma, widow of Joseph Smith, described the process of translating the golden plates thus:
"In writing for your father I frequently wrote day after day, often sitting at the table close by him, he sitting with his face buried in his hat, with the stone in it, and dictating hour after hour with nothing between us"
(Emma Bidamon Smith interview, 1879, available in Vogel, Early Mormon Documents, Volume 1, p. 541)

--- Where are the gold plates here? Where is the curtain between them to hide the plates from the eyes of all but Joseph's. This is not the story we are told in Sunday School. From other evidence, it sounds as though there are a great many stories in the LDS church that are twisted and whitewashed to lure more converts and keep active the members. One prominent example is of Joseph Smith refusing to partake of alcohol when he had surgery on his leg while in his youth. Members are lead to believe Joseph Smith never partook of alcohol, when this is simply not true. There are many instances in the church's history when Joseph Smith liberally partook of alcohol. I’ve read too that just after he “received” the Word of Wisdom, he got in a carriage and cruised around the city drinking a bottle of wine to show that it was just a word of wisdom.
http://www.realmormonhistory.com/smoking,.htm
http://www.xmission.com/~country/reason/w_wisdom.htm
 

• Mormon scriptures contradict each other concerning the forgiveness of murder. Part of being a true prophet is not to contradict yourself regarding basic doctrines and history. Below is an example:

3 Nephi 30:2 -- Turn, all ye Gentiles, from your wicked ways; and repent of your evil doings, of your lyings and deceivings, and of your whoredoms, and of your secret abominations, and your idolatries, and of your murders, and your priestcrafts, and your envyings, and your strifes, and from all your wickedness and abominations, and come unto me, and be baptized in my name, that ye may receive a remission of your sins, and be filled with the Holy Ghost, that ye may be numbered with my people who are of the house of Israel.

vs.
D&C 42:18 -- And now, behold, I speak unto the church. Thou shalt not kill; and he that kills shall not have forgiveness in this world, nor in the world to come.

This is example is a shocking contradiction.
 

• LDS scriptures concerning polygamy very plainly contradict each other:

Jacob 1:15 -- And now it came to pass that the people of Nephi, under the reign of the second king, began to grow hard in their hearts, and indulge themselves somewhat in wicked practices, such as like unto David of old desiring many wives and concubines, and also Solomon, his son.

Jacob 2:24 -- Behold, David and Solomon truly had many wives and concubines, which thing was abominable before me, saith the Lord.

vs.
D&C 132:37-39
      37 Abraham received concubines, and they bore him children; and it was accounted unto him for righteousness, because they were given unto him, and he abode in my law; as Isaac also and Jacob did none other things than that which they were commanded; and because they did none other things than that which they were commanded, they have entered into their exaltation, according to the promises, and sit upon thrones, and are not angels but are gods.
      38 David also received many wives and concubines, and also Solomon and Moses my servants, as also many others of my servants, from the beginning of creation until this time; and in nothing did they sin save in those things which they received not of me.
      39 David's wives and concubines were given unto him of me, by the hand of Nathan, my servant, and others of the prophets who had the keys of this power; and in none of these things did he sin against me save in the case of Uriah and his wife; and, therefore he hath fallen from his exaltation, and received his portion; and he shall not inherit them out of the world, for I gave them unto another, saith the Lord.

Wow, it sounds like Joseph Smith must have really wanted to be polygamous to plainly contradict a book he said was "the most correct of any book on earth."
 
 

• Joseph Smith repeats in translation "mistakes" he says the Bible has. When reading the Book of Mormon, the “Lords Prayer” is almost exactly like it is in the King James Version of the Bible. Yet, in the Joseph Smith Translation of the Bible, Joseph Smith “corrected” a part of the lords prayer. Why does the Book of Mormon, a book that's supposedly the most correct book on earth, have the same “mistakes” that the Bible has.

Book of Mormon:
9 After this manner therefore pray ye: Our Father who art in heaven, hallowed be thy name.
10 Thy will be done on earth as it is in heaven.
11 And forgive us our debts, as we forgive our debtors.
12 And lead us not into temptation, but deliver us from evil.
13 For thine is the kingdom, and the power, and the glory, forever. Amen.

Bible (Joseph Smith translation)
9 Therefore after this manner shall ye pray, saying,
10 Our Father who art in heaven, Hallowed be thy name.
11 Thy kingdom come. Thy will be done on earth, as it is done in heaven.
12 Give us this day, our daily bread.
13 And forgive us our trespasses, as we forgive those who trespass against us.
14 And suffer us not to be led into temptation, but deliver us from evil.
15 For thine is the kingdom and the power, and the glory, forever and ever. Amen.

Bible (KJV)
9 After this manner therefore pray ye: Our Father which art in heaven, Hallowed be thy name.
10 Thy kingdom come, Thy will be done in earth, as it is in heaven.
11 Give us this day our daily bread.
12 And forgive us our debts, as we forgive our debtors.
13 And lead us not into temptation, but deliver us from evil: For thine is the kingdom, and the power, and the glory, for ever. Amen.

One might blow this off as a reasonable human misstep in translation/inspiration, for these are not quite as powerful a contradictions, demanding resolution and explanation as with the polygamy and murder verses. But still, it is odd.
 

• In 600 B.C. when the Book of Mormon is suppose to have begun, it says that the American Indians had steel weapons. I was watching a documentary a while back about ancient American pyramids. It said that the Indians of the Americas cut the stones for their pyramids using certain stones to shape other stones because that didn't have advanced metal technology.
 

• Animals in the Book of Mormon include elephants and horses. Neither of these two animals were found when Columbus arrived in the Americans. This is another case of the Book of Mormon not fitting with historical and archeological findings.
 

• Recent DNA studies confirm that Native Americans are not related to Israelis but to Asians. This is really reasonably obvious. This is plainly, as well, a reason to question the validity of the Book of Mormon and of Joseph Smith being a prophet.
 

• The Book of Abraham has turned out to be nothing that Joseph Smith "translated" or said it was:
    When Egyptologists translated this piece of papyrus, they found that it contained absolutely nothing concerning Abraham. Instead, it turned out to be a pagan funerary text known as the "Book of Breathings," a work which actually evolved from the Egyptian Book of the Dead. The Book of Breathings did not come into existence until the later stages of Egyptian history - just a few centuries before the time of Christ. Like the Book of the Dead, it was buried with those who died in ancient Egypt. It is filled with magic and pagan gods. It was obviously written by a very superstitious people, and is quite different from the religion taught in the Bible.
    The fact that the papyrus Joseph Smith used as the basis for his Book of Abraham is in reality the Book of Breathings cannot be disputed because the name "Book of Breathings" appears clearly on the fourth line of the fragment. In 1968 two Egyptologists from the University of Chicago's Oriental Institute, Professors John A. Wilson and Klaus Baer, identified the papyrus as the "Book of Breathings." A translation by Klaus Baer was printed in Dialogue: A Journal of Mormon Thought, Autumn 1968, pp. 119-20. Professor Richard A Parker, Chairman of the Department of Egyptology at Brown University also translated the papyrus. Professor Hugh Nibley stated that "Parker is the best man in America for this particular period and style of writing."
From: http://www.utlm.org/onlineresources/fallofbookabraham.htm

Along similar lines, the Kinderhook plates sound like they were something created to catch Joseph Smith in the act of his deception. They have been looked at by historians today (Non-Mormon and Mormon) and have been found to be fabrications of the 1800s. Someone created them, made them look old, buried them, pretended to find them and Joseph Smith upon seeing them said they were of ancient origin and was going to "translate" them, but pivotal events happened which lead to him not getting to it.
http://www.xmission.com/~country/reason/kinder.htm
 
 

• The Bible has no teachings about the importance of keeping genealogy to save dead ancestors; perhaps these were just mistranslations, I've checked the Joseph Smith translation and they are unchanged:

     1 Timothy 1:4 - "Neither give heed to fables and endless genealogies..."
     Titus 3:9 - "Avoid foolish questions, and genealogies..."

As I checked other translations (besides the KJV) the 1st Timothy verse plainly is about human genealogies, the Titus verse has perhaps more to do with the genealogy of when in time certain events and scriptural stories took place. Still, the first contradicts Temple logic; yet, I suppose you might argue for the truth of temple ceremonies by that one baptism for the dead verse in the NT (1st Corinthians 15:29). I cannot explain that one, but in that light, the bible there contradicts itself with those two verses, not being internally consistent in itself. Thus, its validity is to a degree certainly in question.
 

• Joseph Smith claimed that he was better than Jesus!

“Come on! ye prosecutors! ye false swearers! All hell, boil over! Ye burning mountains, roll down your lava! for I will come out on top at last. I have more to boast of than ever any man had. I am the only man that has ever been able to keep a whole church together since the days of Adam. A large majority of the whole have stood by me. Neither Paul, John, Peter, nor Jesus ever did it. I boast that no man ever did such a work as I. The followers of Jesus ran away from Him; but the Latter-day Saints never ran away from me yet...When they can get rid of me, the devil will also go.” (History of the Church, Vol. 6, p. 408, 409) -- Joseph Smith: founder, prophet, seer, and revelator of The Church of Jesus Christ of Latter-day Saints.

Also, this quote really says a lot regarding the titanic amount of gloating and pride that JS had in himself.
 

• There is nothing in the New Testament about "eternal marriages" and secret rituals in a temple. The Jewish temple ceremonies are clearly explained in the Old Testament (Exodus, chapters 26-30) and have no relationship to the LDS temple ceremony. And I hear that the temple ceremony was changed earlier this year. Actually, it's changed a lot since Joseph Smith first introduced it, wording changes, garment changes, elimination of the death signs, etc. If it was a restoration of the ancient ways and the rituals, you'd think that over time that they wouldn't change them at all, but want to keep that restoration uncorrupted and unchanged. Perhaps this isn't a reason to not believe Joseph Smith, but it is one to question the validity of the church over time, as is the creation and perpetuation of church wide historical myths, such as Joseph Smith being behind a curtain with the plates while translating and of him never partaking of alcohol.
 

So, overall, looking at the historical oddities, the perpetuated myths and untruths, the blaring internal inconsistencies and contradictions within the Mormon cannon (all by Joseph Smith himself), the archeological and scientific DNA evidence pointing to the Book of Mormon, Book of Abraham, and the Kinderhook plates not being real, the eerie pride of Joseph Smith, temple ceremonies having no relation to those of the Old Testament, and the ordinances changing/corrupting over time --- all clearly point to Joseph Smith, the Book of Mormon, and the church he founded to all be untrue.

As we calmly and honestly look at the evidence, I think the contradictions and disrupted logic are very clear. And in such light, I do not believe that Joseph Smith was a prophet, nor The Book of Mormon to be a true book.