The “in” in “believe in” has two meanings. It may mean “believe that” or “trust.” For example, I may believe in God in the sense that I believe that he exists or in the sense that I believe that he has an effect on my life, ranging from a force to a personal God who has revealed himself as my creator and Lord over my life. As Lord, I trust him, I believe that he is who he has revealed himself to be.
So a Christian believes in Jesus and believes him enough to trust him.? Similarly, a believing Jew believes in God as well as believes God, which are contained in the Hebrew word emunah. There is no need to prove his emunah. “In the beginning” (Genesis 1:1) should be enough, and if not, then the man doesn’t have, according to Martin Buber, a genuine biblical bone in his body. “Biblical man, says Martin Buber, is never in doubt to the existence of God. In professing his faith, his emunah, he merely expresses his trust that the living God is near to him as he was to Abraham and that he entrusts himself to Him” (“Two types of faith” 1962).
Scripture comes alive because God gives it life, and thus it is God who opens the eyes that we may understand. This opening of the eyes is faith. One spends the rest of one’s life adjusting the eyes to the light, keeping in mind that in His light we see the light (Psalm 36:9). What a contrast to Dylan Thomas’ “Rage against the dying of the light” do we find in “Who hath put wisdom in the inward parts.. who hath given understanding to the heart? (Job 38:36). Emunah comprises both Assensus (belief in the sense of mental assent) and Fiducia (trust, personal commitment).
The Reformers of the 16th Century divided true saving faith into three parts: notitia, assensus and fiducia. Notitia comprises knowledge, such as belief in one God, in the humanity (1 John 4:3) and deity of Christ (John 8:24), his crucifixion for sinners (1 Cor. 15:3), and his bodily resurrection from the dead, and some understanding of God’s grace in salvation.
Assensus is belief. This belief hasn’t yet penetrated the heart; it is still on the mental level – a mental assent. “I believe it, that settles it.” Of course, when you say “I believe it, that settles it,” your mental assent is more of a mental descent. To understand why it is a mental descent, you need to ascend to the third level of faith: fiducia.
Fiducia is full trust and commitment, it’s the heart knowledge of Jesus’ prayer to His Father in John 17:
24 Father, I desire that they also, whom you have given me, may be with me where I am, to see my glory that you have given me because you loved me before the foundation of the world. 25 O righteous Father, even though the world does not know you, I know you, and these know that you have sent me. 26 I made known to them your name, and I will continue to make it known, that the love with which you have loved me may be in them, and I in them.”
Notitia (content) is related to our understanding. Without the regenerative life of fiducia (believe in, trust), one is no better off than the devils, who have enough notitia (and assensus) to open a shop. Credo ut intelligam “I believe (in Christ through regeneration) that I may understand” and fides quaerens intellectum “faith (in Christ through regeneration) seeking understanding?” (Anselm of Canterbury).
Martin Buber, the Jewish professor of philosophy, contrasts “belief in” with “trust (in).” Buber says, “Following his leader; Moses comes to the shore, he steps on the sands that are barely covered by shallow water; and the hosts follow him as he follows the God. At this point occurs whatever occurs, and it is apprehended as a miracle. It is irrelevant whether “much” or “little,” unusual things or usual, tremendous or trifling events happened; what is vital is only that what happened was experienced, while it happened, as the act of God. The people saw in whatever it was they saw “the great hand” and they “believed in YHVH” or, more correctly translated, “they gave their trust to YHVH.” (Martin Buber, Moses, (Amherst, NY: Humanity Books. 1988).
Not only the “reformers” (the Protestant Reformation) but all Christian movements understand the distinctions between notitia (content), assensus (accepting the truth of this content, that is, believing that it is true) and fiducia (belief in Christ, or trust in Christ). Jews, and, surprisingly, sometimes “Messianic Jews,” accuse Christians of focusing on “faith” (by which they mean “(mental) assent to” while ignoring trust (Hebrew emunah). Martin Buber’s confusion may help us to understand the unjust criticisms levelled at Christians.
In Romans 3, “faith” is mentioned many times; for example:
21 But now the righteousness of God has been manifested apart from the law, although the Law and the Prophets bear witness to it— 22 the righteousness of God through faith in Jesus Christ for all who believe. For there is no distinction: 23 for all have sinned and fall short of the glory of God, 24 and are justified by his grace as a gift, through the redemption that is in Christ Jesus, 25 whom God put forward as a propitiation by his blood, to be received by faith. This was to show God’s righteousness, because in his divine forbearance he had passed over former sins. 26 It was to show his righteousness at the present time, so that he might be just and the justifier of the one who has faith in Jesus. 27 Then what becomes of our boasting? It is excluded. By what kind of law? By a law of works? No, but by the law of faith. 28 For we hold that one is justified by faith apart from works of the law.
The Christian view of “faith” is summed up in Ephesians 2:8-10 [my square brackets and italics]:
“For by grace you have been saved through faith [in Christ]. And this is not your own doing; it is the gift of God, not a result of works, so that no one may boast. For we are his workmanship, created in Christ Jesus for good works, which God prepared beforehand, that we should walk in them [be faithful “emuna” in them).
“Belief in” in Christianity is always believing in your heart, and putting your complete trust in Christ.