Simply put, to believe in God is to possess confidence in Him. To believe in God includes an acknowledgement of His existence, of course, but true belief in God is more than that. Theism is a great place to start, but it’s not the goal of the journey.
To believe in God is necessary to having religious faith. Scripture says that believing in the true God is foundational to a relationship with Him: “Without faith it is impossible to please God, because anyone who comes to him must believe that he exists and that he rewards those who earnestly seek him” (Hebrews 11:6).
Most basically, to believe in God requires a belief that He actually exists. There are many people around the world who believe in the supernatural world, which would include God or “the gods.” Even if we exclude adherents of pagan religions, there are still many people who believe in a single, personal God. This is an important step, but simply believing that God exists is not enough. As James 2:19 explains, the demons believe in God’s existence as well. Simple acknowledgement of God’s existence does not make one godly.
To believe in God should also involve commitment and a change of life. We all believe facts about things that do not change the way we live. Most people believe the facts that they have been told about the necessity of good diet and exercise, for example, yet most of them do not change their lives on the basis of those facts. Many people who believe that God exists do not do anything in light of that fact, so their belief is really no better than that of the demons. Faith that does not result in actions is a dead faith (James 1:26).
But even a belief in God that motivates one to action is not enough. Some people have a belief in God that consumes their lives. They are driven to great acts of sacrifice, religious devotion, or service in the name of God. In most religions, there are people who are willing to do anything for their god or gods. But, depending on the god in question, the actions demanded of the devotee might include self-harm or even murder. Commitment, service, and devotion to a higher power are no guarantee of moral uprightness.
Genuine belief in God is based on who He really is. The Bible’s axiom that “anyone who comes to him must believe that he exists” (Hebrews 11:6) assumes that faith is placed in the God of the Bible, not some other god. Although many people believe that God exists and want to serve Him, the god they worship is one of their own design. People often remake God in their own image, picking and choosing the aspects of the true God they find agreeable. They may believe that He is love (which is a biblical concept—1 John 4:8), but they may then interpret that by their own definition of love. God, for some, is a doting grandfather who gives them good things and wants them to be happy. Members of Christian cults may be devoted to God, but not God as He has revealed Himself in Scripture. To believe in a god of our own making is a worthless faith. If our belief would conform to reality, we must believe in God as He has revealed Himself: the Triune God who is perfect, omniscient, omnipotent, all-sufficient, immutable, true, faithful, gracious, loving, merciful, holy, and just.
To truly believe in God as He has revealed Himself, we must believe in Jesus Christ, who is “the radiance of God’s glory and the exact representation of his being” (Hebrews 1:3). Jesus is God in the flesh, and it is through Him that God has shown Himself to us in a way we can all understand: “In the past God spoke to our ancestors through the prophets at many times and in various ways, but in these last days he has spoken to us by his Son” (Hebrews 1:1–2). As Jesus said, “Anyone who has seen me has seen the Father. . . . Don’t you believe that I am in the Father, and that the Father is in me? The words I say to you I do not speak on my own authority. Rather, it is the Father, living in me, who is doing his work. Believe me when I say that I am in the Father and the Father is in me” (John 14:9–11).
In modern culture, a generic belief in God and even devotion to God that leads to service of our fellow man is still socially acceptable. However, a more specific faith in Jesus Christ as the supreme and final revelation of God and the only way to God is not socially acceptable. A generic belief in God can unite Jews, Christians, and Muslims of good will. Jesus Christ, however, will divide them (Matthew 10:34). The Bible says that one cannot have faith in God as He really is, unless that faith includes Jesus Christ (John 14:6). If anyone does not honor Jesus Christ, He does not honor God the Father (John 5:23).