Believing that Christ is the Son of God is not enough.
Romans 10:9
“that if you confess with your mouth Jesus as Lord, and believe in your heart that God raised Him from the dead, you will be saved”
James puts the point to the purpose and source of works - it is a demonstration OF our faith. His statement that “works without faith is dead” clearly means just that - it is of no use. This clearly ties directly back to Jesus’ own words regarding Him being the vinedresser - and the unproductive vines being cut off. If you have true faith, but are unproductive/unfruitful (as in-no works), then you are at a very real risk of being cut off . But as Christ Himself said none can pluck His from His hand, that doesn’t mean undoing or losing salvation - it means we may very well be cut off from this life.
Three men die on the cross. Two go to paradise. One was sinless. The second had FAITH. We can’t be sure what happened to the third.
I think we need to better define "believing in Him". I am sure that even Satan believes that Jesus is the Son of God and possesses the ability to forgive all sin, but Satan will not be saved.
You are right , even the demons believe and tremble
An intellectual assent to who Christ is will never save.. We need to have God reveal His holiness to us.. and for Him to bring us to repentance with an understanding that I am a dirty rotten sinner in the eyes of God, no matter how much "good" I do, that I can never appease the wrath of God, or preform any God pleasing act will or approach His Holiness ... Then can we understand and believe that we need a Savior to propitiate our sin before God, and that Savior is Jesus Christ..who paid the sin debt for me...