but we're not talking about dualism. we're talking about whether Jesus died and rose for everyone, or only for those who are old enough to need Him to do this, or who were "weak" enough to need Him to do this, as though if we die young, or are perfect enough on our own, He is somehow superfluous.
what's the danger of believing that man is born perfect, holy and sinless, without need for redemption or grace?
what's the danger of believing that all mankind - regardless of age or understanding - stands in need of the blessed redeeming work that God wrought for us in the eternal Son?
The fallacy in your thinking is "substitution" whereby you believe that Jesus died for something other than the reason He really died and was raised.
I am not contending that a baby is "born perfect and holy." The only reason you think that is because you are caught up in a false dichotomy that of Original Sin whereby you view the "flesh" as evil in and of itself. Thus you look at a baby whom is clearly not "born perfect and holy" and think, "see that proves original sin because the contrary is ridiculous." That is how I suspect your mind is subtly processing such things.
A baby is born NEUTRAL and IGNORANT. A baby is SINLESS therefore INNOCENT because sin only has power through knowledge. Look at what Paul wrote...
Rom 7:8 But sin, taking occasion by the commandment, wrought in me all manner of concupiscence. For without the law sin was dead.
Rom 7:9 For I was alive without the law once: but when the commandment came, sin revived, and I died.
Rom 7:10 And the commandment, which was ordained to life, I found to be unto death.
Rom 7:11 For sin, taking occasion by the commandment, deceived me, and by it slew me.
A baby is NOT born righteous. Vice and virtue are MORAL and pertain to the exercise of the will. Thus one CHOOSES either vice or virtue. A baby is IGNORANT and subject to bodily passions. Those passions are not evil. Augustine taught that those passions were evil because he defined "concupiscence" as an "inherited depravity" which "disabled the virtuous choice." Augustine was wrong, he was influenced via Gnostic philosophy and carried a remnant of it when he converted from the Manichean philosophy to Catholicism.
The natural passions and desires of the flesh are not evil. Evil is when one gives themselves over to those passions in willful disobedience to the influence of God upon their heart. That is "sin unto death" because it cuts one off from "yielding to God" whereby true life is found.
Thus a child has a CHOICE to make when their intellect develops to a state where they can then CHOOSE good or evil. The result of that choice is life and death. Due to the ignorance of the true consequences of sin and due to being born NEUTRAL then there is really no comprehension as to the danger and true depths of evil of sin. Thus it is no wonder that in general every individual will rebel against God at some stage.
This is why we are all responsible and held accountable for our choices by God.
The "redeeming work" of Jesus has to do with the Spirit of His life which we are to "enter into." Not a substitutional sacrifice effecting a legal swap whereby redemption is POSITIONAL. That is deception.
The dualism of Original Sin necessitates an ABSTRACT notion of salvation. It was within the framework of an ABSTRACT notion of salvation that substitution theology developed, first through Anselm in the 12th Century (Satisfaction), then through Aquinus (Penal Punishment), Luther (legal exchange) and finally Calvin and friends (Penal Substitution).