How Can I Know If There Is a God?

A friend of mine has studied many religions--Christian and others. He asked me how he can tell if there is a God.

This is one of the most important questions anyone could ask. Marion G. Romney, an Apostle of The Church of Jesus Christ of Latter-day Saints (commonly called the Mormon Church) said, "No person is, nor can he be, justified in rejecting [the] teachings and commandments, which have been revealed by the Lord, on the basis that he does not know they are true, because everything the Lord does or says has within itself the evidence of its own authenticity, and every person is divinely endowed with the means to discover that evidence and know for himself that it is true" (Marion G. Romney, "The Way of Life," Ensign, May 1976, 81, https://www.lds.org/ensign/1976/05/the-way-of-life?lang=eng).

When Elder Romney made this statement, he was referring to John 7:14-17, which states:
“Now about the midst of the feast Jesus went up into the temple, and taught.
“And the Jews marvelled, saying, How knoweth this man letters, having never learned?
“Jesus answered them, and said, My doctrine is not mine, but his that sent me.
“If any man will do his will, he shall know of the doctrine, whether it be of God, or whether I speak of myself.” (http://www.lds.org/scriptures/nt/john/7?lang=eng)

What the Savior is saying in these verses is that if an individual wants to know the truth of His gospel, they must live the commandments.  Doing so will bring the testimony that is sought.

The means by which that testimony will come is the witness of the Holy Ghost.  As is stated in John 14:26, "The Comforter, which is the Holy Ghost, whom the Father will send in my name, he shall teach you all things."  As we live His commandments, and pray to know if His gospel is true, the Holy Ghost will bear a confirming witness to us.

In the Book of Mormon, a king among the Lamanite people didn't know if there was a God.  He obtained the confirming witness that he sought, in response to this pleading prayer: "O God, Aaron hath told me that there is a God; and if there is a God, and if thou art God, wilt thou make thyself known unto me, and I will give away all my sins to know thee, and that I may be raised from the dead, and be saved at the last day" (Alma 22:18; http://www.lds.org/scriptures/bofm/alma/22?lang=eng).

In answer to this prayer, the king received a witness that what he had been taught was true.  His answer came in a very dramatic way.  Such a powerful witness of the truth is unusual.  For most people, it comes through a quiet, peaceful, confirming feeling.  For those who are sincere and have a desire, as did this king, the answer is sure to come.  Perhaps it won't come all at once, but it certainly will come.