Faith is Intellectual and Assent

The thing is justification and sanctification are to be viewed together. It is not like we become justified by faith and then our sanctification is now done through the law by the Spirit. Many people have grown out of the gospel when it comes to sanctification.
All of this bulks on the fact that Believers are Justified by faith in Christ alone. Faith is in itself rational. It is indeed intellectual. As I have said elsewhere the Hebrew writer says that Faith is creedal.
Gordon Clark says, In his vivid style Kierkegaard describes two men in prayer. The one is in a Lutheran church, and he entertains a true conception of God; but because he prays in a false spirit, he is in truth praying to an idol. the other is actually in a heathen temple praying to idols; but since he prays with an infinite passion, he is in truth praying to God. For the truth lies in the inward HOW, not in the external WHAT. Or, again, Kierkegaard says, 'An objective uncertainty held fast in an appropriation process of the most passionate inwardness is the truth, the highest truth attainable for an existing individual.'

The issue is here that many concern themselves more with the HOW than the WHAT. Scripture tells us to concern ourselves with the What and not necessarily with the How. It does not mean that the How does not matter. The how does matter. But in reality we are speaking of Faith alone and that Christians are justified by faith alone in Christ alone. Faith is concerned with the what for it deals with the mind of Christians. Romans 12 says that it is by the renewing of our mind that we may understand the will of God which is good and perfect and pleasing. Many would want to say that the Mind and Heart are two different things in Scripture. Perhaps, but then they say that heart is more emotions, some would say heart is the seat of the WILL. However, that is not necessarily the case. Here the heart stands for minds. The Christian faith has to do more with the Mind, the intellect.

With that said Gordon Clark has said: The distinction between believing that a chair is comfortable and the act of sitting in it is perfectly obvious. But in the spiritual realm there is no physical action; there is mental action only: Hence the act of sitting down, if it means anything at all, must refer to something completely internal and yet different from belief. Belief in the chair has been made to stand for belief in Christ, and according to the illustration belief in Christ does not save. Something else is needed. But what is this something else that corresponds to the physical act of sitting down? This is the question that is seldom if ever answered. The evangelist put all their stress on sitting down, but never identify its analogue.

James 2 Speaks of those who merely knew that there was one God - from this knowledge (true) they shuddered. However, it was an issue with the content of their faith. These demons did not assent to the truth that God exist and that he is a rewarder of those who seek Him. Faith = Belief That and Belief In.