"Once Saved Always Saved" versus Revelation 3:5

Revelation 3:5 reads “He that overcometh, the same shall be clothed in white raiment; and I will not blot out his name out of the book of life, but I will confess his name before my Father, and before his angels.”How could the doctrine of “once saved always saved” be true if the above verse is true?The same book shows that a person’s name is not written into the “Book Of Life” unless he is saved:

• 20:15 whosoever was not found written in the book of life was cast into the lake of fire
• 21:27 no one will “enter into it (heaven) any thing that defileth, neither … worketh abomination, or maketh a lie: but they which are written in the Lamb’s book of life.”

Revelation 3:5 then necessarily implies that if a saved person does not overcome (temptation, persecution, etc.), if he does not remain faithful, then his name will be erased from the book of life, meaning he will no longer be in a saved relationship with God.Other Bible passages teach the same thing about the book of life. When the Israelites made the golden calf while Moses was on the mount receiving the 10 commandments, God said in Exodus 32:33: Whosoever hath sinned against me, him will I blot out of my book.Only the names of the saved are in the “book of life” to start with. And if it is possible to get your name blotted / taken out of the book of life, then it is clear that it is possible for a saved person to lose his salvation.The doctrine that a Christian cannot “fall from grace” is just plain untrue.