Intellectual assent doesn't save anyone.
Faith, trust, does, and it produces works.
So how do you explain the passage in James in light of Paul's comments here....?
Romans 4:1-25 What then shall we say was gained by Abraham, our forefather according to the flesh? For if Abraham was justified by works, he has something to boast about, but not before God. For what does the Scripture say? “Abraham believed God, and it was counted to him as righteousness.” Now to the one who works, his wages are not counted as a gift but as his due. And to the one who does not work but believes in him who justifies the ungodly, his faith is counted as righteousness, just as David also speaks of the blessing of the one to whom God counts righteousness apart from works: “Blessed are those whose lawless deeds are forgiven, and whose sins are covered; blessed is the man against whom the Lord will not count his sin.”
Is this blessing then only for the circumcised, or also for the uncircumcised? For we say that faith was counted to Abraham as righteousness. How then was it counted to him? Was it before or after he had been circumcised? It was not after, but before he was circumcised. He received the sign of circumcision as a seal of the righteousness that he had by faith while he was still uncircumcised. The purpose was to make him the father of all who believe without being circumcised, so that righteousness would be counted to them as well, and to make him the father of the circumcised who are not merely circumcised but who also walk in the footsteps of the faith that our father Abraham had before he was circumcised.
For the promise to Abraham and his offspring that he would be heir of the world did not come through the law but through the righteousness of faith. For if it is the adherents of the law who are to be the heirs, faith is null and the promise is void. For the law brings wrath, but where there is no law there is no transgression. That is why it depends on faith, in order that the promise may rest on grace and be guaranteed to all his offspring—not only to the adherent of the law but also to the one who shares the faith of Abraham, who is the father of us all, as it is written, “I have made you the father of many nations”—in the presence of the God in whom he believed, who gives life to the dead and calls into existence the things that do not exist. In hope he believed against hope, that he should become the father of many nations, as he had been told, “So shall your offspring be.” He did not weaken in faith when he considered his own body, which was as good as dead (since he was about a hundred years old), or when he considered the barrenness of Sarah's womb. No unbelief made him waver concerning the promise of God, but he grew strong in his faith as he gave glory to God, fully convinced that God was able to do what he had promised. That is why his faith was “counted to him as righteousness.” But the words “it was counted to him” were not written for his sake alone, but for ours also. It will be counted to us who believe in him who raised from the dead Jesus our Lord, who was delivered up for our trespasses and raised for our justification.
Romans 5:1-2 Therefore, since we have been justified by faith, we have peace with God through our Lord Jesus Christ. Through him we have also obtained access by faith into this grace in which we stand, and we rejoice in hope of the glory of God.
Jesus said to his disciples:
“I am the true vine, and my Father is the vine grower.
He takes away every branch in me that does not bear fruit,
[note: the Father can "take away" a branch--i.e. one of us believers--even if that branch is "IN HIM"; this isn't describing an unbeliever. Beliecvers who do not bear fruit will be removed.]
and everyone that does he prunes so that it bears more fruit.
You are already pruned because of the word that I spoke to you.
Remain in me, as I remain in you.
[Why would Jesus urge a believer to REMAIN in Him? To "remain" in Him, they first have to BE in Him, yes? So what does this mean, re: the Protestant idea of "once saved, always saved"? It completely refutes it, apparently... or else Jesus would be absurdly warning His disciples against an impossibility: akin to saying, "Don't you dare create any squar circles, lest you die!" Given the choice between thinking that Jesus has "lost it", and thinking that the "once saved, always saved" proponents are dead wrong, I'll always choose the latter.]
Just as a branch cannot bear fruit on its own unless it remains on the vine, so neither can you unless you remain in me.
[Remaining in Christ is a free choice, and refusing (or neglecting) to remain in Him leads to us failing to bear fruit... which has bad consequences for teh believer who does that.]
I am the vine, you are the branches.
Whoever remains in me and I in him will bear much fruit,
because without me you can do nothing.
Anyone who does not remain in me
will be thrown out like a branch and wither;
people will gather them and throw them into a fire
and they will be burned.
[This doesn't sound like Heaven, to me; rather, it sounds like hell and eternal damnation. Those who WERE "in Him", but who do not REMAIN in Him and produce fruit, will be thrown out, gathered, thrown into the fire, and burned. This is serious.]
If you remain in me and my words remain in you,
[Again: note the "IF"? It is no "automatic guarantee"--we have to REMAIN in Him, and we have to let His Word REMAIN in us, on pain of being thrown into the fire. This is Jesus talking, not me!]
ask for whatever you want and it will be done for you.
By this is my Father glorified,
that you bear much fruit and become my disciples.”
[A believer need not be a true disciple; one can be a mere "hearer"--and even a believer--of the Word, and deceive Himself, as St. James warns (James 1:22ff). If we are not "doers that act" (James 1:25), we deceive ourselves, and the consequences are grave... as described by Our Lord, above.]