I Know What Is True Because We Have a Living Prophet to Tell Us the Truth

This FAQ addresses the question of personal responsibility for knowing truth

The Infallible Prophet:

It is a given that LDS members hold the Living Prophet in great esteem.  When a person desires to know what is ‘truth’ he or she defers to the prophet’s words as the highest authority.  This choice is in concert with LDS teachings.  “Teachings of the Living Prophets” (an Institute textbook for Religion 333) records:

Page 15: In conclusion, let us summarize this grand key, these "Fourteen Fundamentals in Following the Prophet," for our salvation hangs on them.
     First:      The prophet is the only man who speaks for the Lord in everything.
     Second: The living prophet is more vital to us than the standard works.
     Third:     The living prophet is more important to us than a dead prophet.
     Fourth:   The prophet will never lead the Church astray

Page 20: No man ought to contend for what is in the books, in the face of God's mouthpiece, who speaks for him and interprets his words. To so contend is to defer to the dead letter in preference to the living oracle, which is always a false position.

Given these teachings of infallibility and highest authority, individuals cannot argue (“contend”) with the words of the prophet even when using scripture (“what is in the books”). This places a great responsibility on the Living Prophet for what individuals hold as truth.