The apostle Paul makes a statement in his letter to the church at Ephesus which has more meaning than is easily recognized.
"For by grace are ye saved through faith; and that not of yourselves: it is the gift of God:" (Ephesians 2:8 KJV)
Now is it faith, or is it grace, or both, or neither which actually saves us? It is not either that saves us by itself. Nor is it both unless much more is involved. Unfortunately, far too many people have too much confidence in simply believing something or other. Biblical faith is described as: "...the substance of things hoped for, the evidence of things not seen." (Hebrews 11:1 KJV)
But even that description does not fully explain what is involved in Biblical faith. To have saving faith, one must believe the Bible is the word of God and that Jesus Christ is His Son. He must believe that the teachings of Jesus and his inspired writers are true and must be obeyed. That is biblical faith. Simply believing God exists and even that Jesus is His Son, even though a good start, is inadequate. Obedience of God's word is an inferred imperative. Read this following verse of scripture:
"Nevertheless among the chief rulers also many believed on him; but because of the Pharisees they did not confess him, lest they should be put out of the synagogue:" (John 12:42 KJV)
Regardless of how strongly you believe in Jesus, if you are unwilling to confess him, you remain as lost as an unbeliever, here's more proof of that:
"Also I say unto you, Whosoever shall confess me before men, him shall the Son of man also confess before the angels of God: But he that denieth me before men shall be denied before the angels of God." (Luke 12:8 KJV)
Another factor is that faith alone will not save you. Here is a plain English explanation of that which cannot be misunderstood without a lot of help:
“But wilt thou know, O vain man, that faith without works is dead? Was not Abraham our father justified by works, when he had offered Isaac his son upon the altar? Seest thou how faith wrought with his works, and by works was faith made perfect? And the scripture was fulfilled which saith, Abraham believed God, and it was imputed unto him for righteousness: and he was called the Friend of God. Ye see then how that by works a man is justified, and not by faith only. Likewise also was not Rahab the harlot justified by works, when she had received the messengers, and had sent them out another way? For as the body without the spirit is dead, so faith without works is dead also.” (James 2:20-26 KJV)
One may also firmly believe that Jesus is God's Son and that he died for our sins, yet if he errs from that faith, he can lose his soul.
“For the love of money is the root of all evil: which while some coveted after, they have erred from the faith, and pierced themselves through with many sorrows.” (1 Timothy 6:10 KJV)