I would like to deliberately distinguish between the term and meaning of belief versus faith and the false claim by some that we must enter into Christ in belief...
As true converts in Christ we do not just believe ON or IN Christ, we have the saving faith IN our spirit with Christ in us. We are already one in and with Christ.
And there is ONLY ONE type or form of spiritual faith we practice and possess. It is the faith that saves, where we have FAITH IN Christ's spirit who entered into us along with his Father on the day, hour, minute and second, and moment of our miraculous spiritual conversion - as a new spiritual creature. We have faith IN Christ because Christ has already entered INTO us and we are IN Him.
We never enter into Christ. If we believe, without possessing saving faith, that we must enter INTO Christ to be IN Christ and to remain converted, then this activity is of the carnal mind and one of self-work. Attempting to keep entering into Christ is from one who is unconverted, and will never produce or cause genuine conversion and salvation, let alone wanting a closer walk with God through Christ's spirit, influencing and changing them everyday. We cannot never force conversion or salvation by believing in entering INTO Christ's spirit. The Father can only perform this miraculous act by entering into us to the new life. We first believe, then we, the chosen, are given faith as a gift from God to salvation.
At the moment of conversion the Spirit of God places the spirit of his Son within us. HE enters INTO us, not the other way around. We can do nothing to enter INTO Christ, no matter how hard we try.
All seekers in Christ must go beyond just believing ON and IN Christ. They need the saving faith in spirit! And then this saving faith develops and grows in degrees over time. There are levels or stages of saving faith that we progress into and dwell in - from little faith, growing faith, mature faith to moments of strong, great and unwavering faith that all believers can experience. They are all based on ONE level of faith however, the precious saving faith.
(Rom 12:3) I realize how kind God has been to me, and so I tell each of you not to think you are better than you really are. Use good sense and measure yourself by the amount of faith that God has given you.
Each one in Christ is given a measure of this saving faith suited for his or her purpose for God.
If we are truly in Christ then we are anointed, set aside by God himself for his purpose. And to be anointed and chosen we MUST have this saving faith and not just a belief IN Christ or ON Christ. A belief is more of a mental activity compared to a spiritual faith.
All in the Body of Christ has the SAME saving faith, and varies only in the amount or strength.
Romans 12:4-5 (NKJV)4 For as we have many members in one body, but all the members do not have the same function,5 so we, being many, are one body in Christ, and individually members of one another.
2 Corinthians 1:21-22 (NKJV) 21 Now He who establishes us with you in Christ and has anointed us is God,22 who also has sealed us and given us the Spirit in our hearts as a guarantee.
We do not need to try and keep going INTO Christ. We are already there! We just need to keep trusting in the spirit of Christ with us. We will be amazed how our faith matures as we yield more and more of our life over to Christ, in spirit.
(2Th 1:3) My dear friends, we always have good reason to thank God for you, because your faith in God and your love for each other keep growing all the time.
(Rom 10:17) No one can have faith without hearing the message about Christ.
As one source has said, Active faith is unquestioning belief, trust and reliance upon God with all confidence. Faith can become as real as any of our senses.