When we reject true prophets, who see by the light of revelation, and follow instead those who have no divine light, we are really following "blind guides" (Helaman 13:29) President Marion G Romney, who was a member of the First Presidency said: Those who profess to accept the gospel and who at the same time criticize and refuse to follow the counsel of the prophet are assuming an indefensible position. Such a spirit leads to apostasy." (Conference Report, April 1983) President Ezra Taft Benson taught:" How we respond to the words of a living prophet when he tells us what we need to know, but would rather not hear, is a test of our faithfulness". (Fourteen Fundamentals in Following the Prophet, in 1980 Devotional Speeches of the Year)
This is when our faith in a living prophet called by God comes into play. But how do you know if it is faith or just belief?
Belief can be passive, merely an acceptance that something is true, while faith is active. Faith requires belief and trust. It gives us confidence and conviction and moves us to action. We cannot have faith without belief, but we can believe and not have faith. It is not enough to just believe in Jesus Christ. For the gospel to bless our lives we must have faith that motivates us to follow Him. Knowledge, like belief, needs action in order to benefit us. Simply knowing that something can help or harm us does us no good unless we act on that knowledge. There is special knowledge that comes when we exercise faith and seek to live the gospel. When we act upon our beliefs with faith, the spirit touches our heart and mind. We receive a spiritual witness from the Holy Ghost that enables us to say "we know" that Christ is our Savior and that the Church is true. (see James E. Talmage, Articles of Faith , pg 96-100)