Jeremiah 1:5 is sited by Mormons as a proof text for our existence before being physically born into this world, as though the phrase "I knew thee" meant not the foreknowledge of God but that He knew Jeremiah in another world or existence. Using this logic, Matthew 7:23 would mean that those being condemned at judgment never really existed because God will say, "Depart from me, I never knew you." Likewise Acts 15:18 would mean that the world and all of God's creation existed before He created it because "Known unto God are all His works from the beginning of the world."
Please see Genesis 2:7; John 3:31, 8:23; Romans 9:11 and 1Corinthians 15:46 for the truth on the subject. These verses show again the clear choice each Mormon must make...the word of God as recorded in the Bible or the confused, contradictory word of a false prophet.