A possible helpful question could be, "Can one truly believe in Christ's earthly life (1Jo 4:3; 2Jo 1:7) and His resurrection (Rom 10:9) and also truly believe this alone is insufficient for salvation? I believe while we are in an unregenerate state, we can only desire to believe in God (which I believe also comes from Him - John 6:44) because it cannot truly become practical until He imparts faith through His Spirit during regeneration, which of course must be preceded by first being aware of the Gospel essentials for faith (listed above). For it stands to reason that it requires knowing what facts are to be believed in before believing in them can become a practicality. Once essentials are known, God is approached in prayer request for salvation and upon the Spirit entering the seeker's life (if sincere), His fruit (Gal 5:22 - not fruits, it's a singular package which includes faith, different from the ministerial gift of faith - 1 Cor 12:9) begins to take effect, as "The Spirit Himself bears witness with our spirit that we are children of God" (Rom 8:16). The Spirit's personal "witness" or confirmation of faith in Christ is continually affirmed in us, without which such a conviction and gradual convincing of faith is not possible. This permanent consoling of the Holy Spirit is where faith not only takes root but grows--but only through Scripture. I believe it would not be possible for the Spirit of God to be neglectful in allowing the new-born to continually walk in ignorance of Christ's sufficiency. If one truly believes in an error, e.g. that works are also required for receiving salvation, I believe it may evince one of two possibilities; a temporary unawareness of this truth, in which it's just a matter of time before the Spirit reveals it; or there was not a true desire for salvation upon request (James 4:3), thus the absence of the Spirit.