Faith as the quality by which one believes may be defined as a mental appreciation of, and a heart’s reliance upon, certain objects. This definition is based upon St. Paul’s statement, “Faith is assurance of things hoped for, a conviction of things not seen” (Heb. 11:1, A.R.V.; see also R.S.V., Rotherham, Young’s Literal Translation, etc.). It will be noticed that the Apostle here gives the matter in reverse order to its actual development or unfolding, for he gives the heart’s reliance (the assurance or confidence in things hoped for) first, and the mental appreciation (the conviction, based upon the evidence or attestation of God’s Word concerning things not seen) last.
Thus, in reverse order, the Apostle shows that there are two parts to faith: one of these is exercised by the mind—mental appreciation, and the other is exercised by the heart—heart’s reliance. Neither of these can be absent in a genuine faith. Mental appreciation must be present as the foundation, and heart’s reliance as the superstructure. Both are necessary to the house of faith, as a natural foundation and superstructure are necessary to a natural house. A believing Christian exercises as his faith a mental appreciation of, and heart’s reliance upon, God and Christ in respect to Their persons, characters, words and works.
Faith is trusting in something. We trust that the Bible is the word of God, that God was able and willing to communicate to us through writings of the prophets and apostles (and other prominent Christians of the day) - so faith is an assumption about what the Bible is, and what it teaches. I'm referring to Paul's statement that Christ delivers us from the body of death, Rom. 7:24, in which he says in 8:2 that we are free from the principle of sin and death. But by saying that Christ freed us from the nature of sin, I'm also taking into account 1 John 3:9 in which I believe John is saying that the Christian living in faith is living a lifestyle of repentance, in which sin has largely receded from his life, and he continues in the direction of holiness by faith that comes from God. It's the idea that the Christian is being released from the power of the sin nature, that is, progressive sanctification that characterizes the Christian life. This is my take on Paul's phrase "believes unto righteousness." I take it to mean righteousness not only positional, but also (to some extent) formational. And the way that righteousness is formational is that the Holy Spirit puts it in our hearts to thirst for it in our lives.
So, when Paul wrote "with the heart man believes unto righteousness," he is talking about assuming that Christ has delivered us from the nature of sin (that is, the principle thereof), which is the same as using our imagination to reach out to God for making us righteous. If we are in Christ, then we are reaching to God with heart-faith for righteousness. And since deliverance from the sin principle is ongoing in this life, we continue living this heart-faith. I'm referring to Jesus' statement "blessed are those who hunger and thirst for righteousness, for they shall be satisfied." So I'm speaking experientially, as opposed to judicially. So then, we seek experiential righteousness from God by faith. Granted, a right standing with God (justification) is imputed from regeneration (I take this to mean judicial, or positional). But how does that imputed justification/righteousness fulfill the individual, unless they experience something internally that they can associate with positional righteousness? When Jesus says "they shall be satisfied," I take that to mean that they experience what they long for, that peace with God becomes heart-felt, and a motivator for obedience to God's will, namely loving their neighbor with a God-kind of love.
"With the heart man believes..." - meaning that we actively imagine God helping us live at all times. So God is with us at all times, and not someone "out there, demanding we do things by our own strength and willpower". So the ethical commands aren't "do this or be condemned," but rather "Christ has done so much for us, that we are so grateful as to love Him with all our heart, to do whatever He says.
"...unto righteousness" - so that our right standing with God is not merely a position in Christ, but is an active and vital role that God is producing right living through us. And here is James also using the idea, since he says "faith without works is dead." He is emphasizing that the right kind of faith is that kind which obeys Christ's command to love others in a practical way. Yet, when he says "faith without works," he is stooping to the level of the gnostics (or whoever is claiming to have faith in the wrong way) in his usage of the term, in order to distinguish between the claim of faith and actual faith in Christ. James is rebuking people for the wrong usage of the term "faith." I'm agreeing with James that "faith without works is dead," - that is, a so-called faith that is a claim to believe in Jesus, but does not trust Him enough to do what He says, is merely a fantasy. This is not to define salvation or explain the process of sanctification. The focus is only on faith, and what exactly is it that justifies us with God.
And we can see the same idea taught by the writer of Hebrews (a third witness) when he wrote about those people who died in the wilderness of Numbers, saying about their unbelief "they did not mix what they heard with faith." (Heb. 4:2 - I come to this paraphrase after comparing different translations). He uses the term faith in the same manner. He is talking about the failure of the nation to obtain rest, which is a type of the spiritual Jew who fails to obtain rest because of unbelief, which I take it to mean that the Jewish Christian doesn't get assurance of his salvation in Christ because he has a residual belief in his mind that he has to sacrifice animals to obtain atonement for his sins. This is how I read Hebrews. And so, in application to the Christian life, he is saying in ch. 4 that the Christian fails to enter rest (that is, assurance of salvation) because of doubting the sufficiency of Christ's sacrifice. Thus, my statement that his usage of the term faith is the same as Paul and James' usage. I believe that his description of it in ch. 11 shows his understanding that faith is trusting God.
So what James is writing against is the idea that someone having faith in Christ can do just anything they want (namely practice class prejudice) and still be saved. He is saying that's not real faith in Christ, and that's why it's "dead." Someone having real faith is going to love their neighbor in the same way that Christ does and commanded us to do. Since the Reformation, the term "antinomianism" has been applied to the hypothetical behavior that James is rebuking. I am using the phrase "class prejudice" to refer to James' rebuke of people who neglect the needs of others, or place rich people in privileged positions while excluding the poor. Such people have not obeyed Christ concerning loving one's neighbor. But the "real faith" that James is advocating does obey Christ because of their motivating faith.
This is the only kind of faith that makes “sola fide” correct in the Biblical framework. “Sola fide” is one of the “sola”s of the Reformation. It's the only kind of faith that measures up to what the whole NT is about. I'm contending against the idea that the “fide” in “sola fide” means generic faith. I'm debating that faith in this context is not generic the way the world uses the term, which is the error of the Catholic and Orthodox churches (in addition to many Protestants). Rather, it is faith that is heart-felt and motivates obedience to Christ's commands, because it is an inherent trust in His integrity, words, and promises.
Therefore, faith is trusting in something. Christians trust in God, and believe the Bible is true, whereas atheists trust in themselves, and believe their opinion is true.