There is a teaching that one need only mentally ascend, that is acknowledge, God to be saved. Often scripture is quoted out of context to support this errant philosophy.
TO "believe" only, alone, is not what Paul or the other Apostles taught: they taught to believe enough to follow God's instructions for our salvation, not merely "believe" by making a mere verbal acknowledgement and then go on as we always have before.
King James Version (KJV)
17 Even so faith, if it hath not works, is dead, being alone.
18 Yea, a man may say, Thou hast faith, and I have works: shew me thy faith without thy works, and I will shew thee my faith by my works.
19 Thou believest that there is one God; thou doest well: the devils also believe, and tremble.
30 And brought them out, and said, Sirs, what must I do to be saved?
31 And they said, Believe on the Lord Jesus Christ, and thou shalt be saved, and thy house.
32 And they spake unto him the word of the Lord, and to all that were in his house.
33 And he took them the same hour of the night, and washed their stripes; and was baptized, he and all his, straightway.
And Crispus, the chief ruler of the synagogue, believed on the Lord with all his house; and many of the Corinthians hearing believed, and were baptized.
Acts 19:4 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.
But when they believed Philip preaching the things concerning the kingdom of God, and the name of Jesus Christ, they were baptized, both men and women.
Then Simon himself believed also: and when he was baptized, he continued with Philip, and wondered, beholding the miracles and signs which were done.
In every case in the Word of God, believing involves a genuine, real, faith that results in following instructions. Those who are recorded in scripture as believing immediately follow God's instructions for their salvation and are Baptized using the actual Name of Jesus so that their sins really are removed from them.
God looks for faith that results in obedience, the kind the original Church that God established demonstrated. Believe God enough to follow HIS instructions for your salvation too!
Acts 2:37 Now when they heard this, they were pricked in their heart, and said unto Peter and to the rest of the apostles, Men and brethren, what shall we do?
38 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.
39 For the promise is unto you, and to your children, and to all that are afar off, even as many as the Lord our God shall call.