Is salvation contingent upon a decision to believe on Christ? Or is salvation based on more than a human decision? If it is based on a human decision to believe, does that mean everybody who has decided to believe in Jesus is a Christian? Is it a certain type of belief that has to be really strong or sincere? Does a person have to believe the right things and deny the wrong things? My contention is that not everyone who says they are a Christian is really a Christian and that sincerity or strength of belief even in the right things have nothing to do with it. Salvation is grounded on more, much more than merely a human decision, but rather it is a decision that starts with God, resulting in an action on God’s part whereby he sent his son Jesus to live a perfect life and die as a perfect substitute for people. But he didn’t stop there he also sent the Holy Spirit to regenerate (gives new life to) all that a spiritually dead human being is (a persons thoughts, affections, and will) which results in that person clinging to Christ. Christ is the grounds of salvation but faith is the conduit by which the sinner is connected to Christ. But not just any faith, a saving faith. Dead faith anyone can have, even demons have that kind of faith, that is knowing and believing. Demons know and believe who Christ is. But a saving faith is different, it does not originate with the person. A saving faith originates forth from a person whose mind and heart and will has been changed by God (that is God the Holy Spirit). So you could say Christ is the grounds for salvation and a decision for Christ grounded in the Holy Spirit is the grounds for being connected to Christ.
Bottom line; a person can make decisions all they want but unless they spring from a heart that has been given life by the Holy Spirit, those decisions means nothing. Decisions made from an unregenerate, unborn again, natural fleshly heart are sinful, self centered, selfish and self-serving at best. Because that is what an unborn again heart is corrupted with; sinful self serving, self centeredness. Without the Holy Spirit opening an unbelievers eyes an unbeliever is blind to who they are in their sin and to who God is in his holiness - thus they are blind to their need for salvation and how it happens. “In their case the god of this world has blinded the minds of the unbelievers, to keep them from seeing the light of the gospel of the glory of Christ, who is the image of God.” (2 Corinthians 4:4) One must be born again or they cannot see the kingdom of God (John 3:3) A natural born man or woman brings forth natural decisions and a born by the Spirit man or woman brings forth good and right and meaningful spiritual decisions. “That which is born of the flesh is flesh, and that which is born of the Spirit is spirit.” (John 3:6)
Salvation is never evidenced by less than a human choice for all that God is in Christ Jesus but it always involves more than that and is never contingent upon it.
A good decision cannot come from a corrupt heart. If the Holy Spirit is not in it, it means nothing. One must be given a new heart first. Salvation starts and ends with God and is evidenced by Spirit filled faith and hope in Him, that includes a desire to live for and have a surrendered life to Him. “these are the things God has revealed to us by his Spirit. The Spirit searches all things, even the deep things of God. For who knows a person’s thoughts except their own spirit within them? In the same way no one knows the thoughts of God except the Spirit of God. What we have received is not the spirit of the world, but the Spirit who is from God, so that we may understand what God has freely given us. This is what we speak, not in words taught us by human wisdom but in words taught by the Spirit, explaining spiritual realities with Spirit-taught words. The person without the Spirit does not accept the things that come from the Spirit of God but considers them foolishness, and cannot understand them because they are discerned only through the Spirit.” (1 Corinthians 2:10-14)