the majority of Christians today operate in mental assent. mental assent is a state of mind where one may appear to believe something, but does not act on what they claim to believe. it agrees with God but does not believe God. Christians, who operate in mental assent, read the word of God and claim that they believe it, but when something comes up, they don't act on it.
read and study James 2:17 and 18 for clarification