The New Testament begs the ultimate question in Johannine and Pauline literature. That is, what is it we’re supposed to believe when believing in Christ. Many will note what Paul teaches and says ought to be taught (Christ’s death and resurrection), however, it is a stretch to suggest this is what Paul or John means in terms of justification. Symbolically, the death and resurrection of Christ is about identification, through baptism just as the Eucharist is; participation in the life of Christ. And for Paul at least, it is the hope, not the fact of resurrection that means something to us.
At least for Paul, it is only clearly implied that we understand God and humanity through Christ, and this is his most heartfelt conviction. Formulaically, Paul entails justification with a mere proclamation of God, though the ramifications and effects of this are profoundly transformative. In John as well, Jesus is the manner, mode, and truth of both man and God.
Most protestants, particularly Calvinists, answer the question from someone else’s supposings and then read that into what either Paul or John have actually said. In that case, where the “believe in Him” is often literalness and taking talk of miracles as historical and necessary things to take as true for salvation, we ought to ask what difference that makes to us or to God.
In the case of the former, believing Jesus perfectly reflects the fullness of divinity and of humanity, we are given hope that for all we are, God loves us, and that for all He is, we can trust his mercy and grace, which begins in us something remarkable.
It seems to me that the question begged as to what we are to believe about Christ that is life changing shouldn’t be met with an answer that begs yet another question of why that answer matters or how it does or could.
Just a thought.