(From Chapter 3 of The Christian’s Great Interest, by William Guthrie)
Belief is the condition upon which God grants salvation. If we believe, we will be saved. Moreover, belief is evidence that we have been saved. If we can see that we have true faith in Jesus, then we can know that we have a saving interest in Jesus.
The first thing whereby men may know it is, their closing with Christ in the gospel wherein He is held forth. This is believing, or faith, which is the condition of the covenant: ‘It is of faith, that it might be by grace.’ (Rom. 4: 19.) Believe on the Lord Jesus Christ, and thou shalt be saved.’ (Acts 26: 31.)
However, many make mistakes about the nature of true faith. He explains that true faith is a paradoxical thing: It is both a matter beyond human ability and a thing within the grasp of any child. The reason for this paradox is that is not a mere matter of intellectual assent, faith is also a matter of desire.
We all believe, constantly and in many things. For example, we must believe that we exist, that others exist, that the speech we hear is intended to communicate information, that the universe was not formed complete with our memories three minutes ago, et cetera. Until we believe, we cannot know anything. Thus, in an important sense, belief comes before any knowledge.
Thus, in asking us to believe, God merely requires we do something we do naturally and repeatedly in all parts of our lives. God does not ask for something above us or beyond us. God does not ask us to ascend into heaven or to dig down into hell, he merely asks that we believe:
6 But the righteousness based on faith says, “Do not say in your heart, ‘Who will ascend into heaven?’ ” (that is, to bring Christ down) 7 “or ‘Who will descend into the abyss?’ ” (that is, to bring Christ up from the dead). 8 But what does it say? “The word is near you, in your mouth and in your heart” (that is, the word of faith that we proclaim); 9 because, if you confess with your mouth that Jesus is Lord and believe in your heart that God raised him from the dead, you will be saved. 10 For with the heart one believes and is justified, and with the mouth one confesses and is saved. 11 For the Scripture says, “Everyone who believes in him will not be put to shame.” Romans 10:6–11 (ESV)
Yet, at the same time, true saving faith lies beyond us. We cannot believe rightly, unless God grants us the gift of true saving faith:
44 No one can come to me unless the Father who sent me draws him. And I will raise him up on the last day. John 6:44 (ESV)
29 For it has been granted to you that for the sake of Christ you should not only believe in him but also suffer for his sake, Philippians 1:29 (ESV)
How then can faith be both simple and impossible? Let me give two examples. It is the easiest thing in the world to love another human being. Human beings do this naturally and repeatedly. Parents naturally love their children. Children naturally love their parents. People come to love one another and to marry with some regularity.
Yet, I cannot imagine not loving my wife and loving another woman in her place. I cannot imagine not loving my children and loving other children their place. At one level, showing affection is quite simple. Yet, when considered from a different direction, it is an impossible matter.
The act of driving an automobile is quite simple. Millions of people drive cars every day. However, if I were to ask (most) of these people whether they could drive their car into a crowd of children, they would say “No.”
You see, a matter may be simple as a matter of physical or emotional action, and yet impossible as a matter of desire. Since true saving faith consists of desire, it is an impossible and simply matter at once.