Can a Chrisitan lose his/her salvation?

[Jehanne]

So, the Saved set is a proper subset of the Elect set then?

To put it simply, yes.

As for the Catholic Church & Baptism, many Protestants (such as Anglicans) baptize using the Trinitarian formula ("In the name of the Father..."); are you saying that they are wrong, also?  And, why should we believe your interpretation of the Bible as opposed to someone else's?  And, does not the end of the Gospel of Matthew state to "Baptize in the name of the Father and of the Son and of the Holy Spirit"? (Matthew 28:19)

Yes, Jesus did state to baptize in the NAME of the Father and of the Son and of the Holy Spirit, but ask yourself this; is Father, Son or Holy Spirit a name? Those are not names but titles, the name of the Father, Son, and Holy Spirit is Jesus Christ.

Having three different titles does not make one three different personalities...

The Jehovah of the Old testament is the Jesus of the New testament.

And God said unto Moses, I AM THAT I AM: and he said, Thus shalt thou say unto the children of Israel, I AM hath sent me unto you.- Exodus 3:14

Jesus said unto them, Verily, verily, I say unto you, Before Abraham was, I am. - John 8:58

In Revelation Jesus stated

I am Alpha and Omega, the beginning and the ending, saith the Lord, which is, and which was, and which is to come, the Almighty. - Revelation 1:8

Did not Jesus give Peter the keys to the Kingdom of Heaven? When the people asked Peter essentially how to get to Heaven, he told them to be baptized in the name of Jesus Christ, THAT IS THE KEY!

Then Peter said unto them, Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Ghost. - Acts 2:38

When Paul met those that were baptized by John the Baptist they had to be re-baptized in the name of Jesus Christ.

Acts 19:3-5

3 And he said unto them, Unto what then were ye baptized? And they said, Unto John's baptism.

4 Then said Paul, John verily baptized with the baptism of repentance, saying unto the people, that they should believe on him which should come after him, that is, on Christ Jesus.

5 When they heard this, they were baptized in the name of the Lord Jesus.

Now find me one place in the Bible where anyone was baptized under the titles of Father, Son, and Holy Spirit...

If you can't then you must acknowledge that to baptize in that manner is contrary to scripture.

Show me where the Trinity is taught in the Bible.  How about the books of the Bible themselves?  Why is the Gospel of Peter not part of scripture?  Or, the Gospel of Thomas?  Or, the Acts of Pilate?