Once Saved Always Saved?

This is a crucial question. Is a person who is saved saved forever? Can a saved person lose their salvation?There are four responses to the Gospel:No response, an initial response that dies when trouble comes, a response that allows the cares of the world to quench the word and a fruitful response to the Gospel. The fourth response is the one who remains saved. We know that we are saved if we love the brethren.
Not everyone who hears and responds to the Gospel is saved but the one who remains in fellowship and perseveres is saved. We know that if we believe that Jesus is the Son of God and that God raised Him from the dead we are saved. Many start but not all of them finish. Only the person who does not fall away and perseveres is saved. So this person once saved is always saved.