It would be impossible to overstate the importance of faith because “without faith it is impossible to please [God]” (Heb. 11:6a). Given the eternal consequences, we can see why it is important for us to understand faith clearly. As is often the case, in seeking to understand what faith is, it is helpful to consider what faith is not.
Faith is not just positive thinking. Sadly, many Christians seem to feel that when the Bible speaks of faith, it is telling us that we should just choose what we want (usually health or wealth) and then believe really hard and God will be obligated to give it to us. So-called “faith healers” and the prosperity-obsessed televangelists have promoted this idea (adding, of course, the small twist that in order to prove your faith, you are supposed to send them money). Such thinking is utterly misguided. True faith is not in our whims or desires; biblical faith is always based on the Word of God (Rom. 10:17). We can trust what God says, not what our deceptive hearts crave.
Faith is not mere intellectual assent. “You believe that God is one. You do well; the demons also believe, and shudder” (Jas. 2:19). The demons believed a great many true things about Christ. They knew He was the Son of God (Lk. 8:28). They knew He was absolutely holy (Mk. 1:24). They knew He was sovereign over them and would condemn them to eternal torment in the end (Mt. 8:29). But merely acknowledging certain facts is not faith. Similarly, there are many religious people who have spent a lifetime believing true things about Jesus who have never trusted in Him and, consequently, are not saved.
Faith is not a new way of salvation. There were those in New Testament times who thought that people used to get saved by the Law but that Christianity presented a new way of salvation: faith. But Romans clearly demonstrates that nobody was ever saved by works. As an object lesson, Paul chose two heroes of Judaism and showed that Abraham and David were both saved by faith (Rom. 4). And he proved it from the Old Testament! Salvation has never been by works because “because by the works of the Law no flesh will be justified in His sight” (Rom. 3:20).
Faith is not blind. Opponents of Christianity enjoy claiming that faith is mindless and irrational. Supposedly, Christians are blindly stumbling from one fantasy to the next with no evidence to justify any of it. Again, this betrays an utter ignorance of what the Bible means by faith. Christians make one assumption: the Bible is the Word of God. From this assumption (for which there is overwhelming evidence), flow all of our beliefs concerning God, man, sin, salvation, heaven, hell, life, and death. In contrast, the unbeliever is awash in a sea of countless assumptions and wishful thinking. Who is operating by blind faith: the person whose beliefs flow from one eminently defensible assumption, or the person whose beliefs are an endless string of guesses and I hope so’s?
Faith, simply, is trusting Christ. It means to stop relying on ourselves (e.g. Lk. 18:9) either for salvation or for the strength and wisdom to serve the Lord, and to rely on Christ. What a relief to be able to stop depending on ourselves and depend on His perfect Son instead!