It is the Lord's work, and I plead with you not to forget it. I implore you not to disbelieve it; for it is true. All that the Lord said concerning this latter-day work will come to pass. The world cannot prevent it. The blind that will not see, the deaf that will not hear, cannot prevent the work from going on. They may throw blocks before the wheels, they may ridicule, they may malign, they may stir up the spirit of persecution and bitterness against the Saints, they may do all in their power to deceive the people and lead them astray; but God is at the helm, and he will lead his people to victory. Men and women may be deceived by the craftiness of the adversary and by the spirit of darkness that is in the world; they may be deceived with Christian Science, with hypnotism, with animal magnetism, with mesmerism, with spiritualism, and with all the other man-made and demon-stimulated isms which exist in the world; but the elect of God shall see and know the truth. They will not be blind, because they will see; they will not be deaf, because they will hear; and they will walk in the light, as God is in the light, that they may have fellowship with Jesus Christ and that his blood may cleanse them from all their sins.
President Joseph F. Smith, Gospel Doctrine
Whether or not a person believes in the gospel of Jesus Christ, whether or not they even believe in God or Jesus Christ, or whether or not a person has succumbed to societal influences, does not, I repeat, does not mean that it is not true.
That's like saying that the sun doesn't exist just because we are blind and we can't see it. Or, just because we never experienced snow, doesn't mean it doesn't fall. Or, just because we've never been to the beach, doesn't mean the ocean is not real.
The truth of the gospel, the existence of God is as real as the ground under my feet. Or the wind in my face. Or anything that is tangible and explainable. But...just because we can't explain it, doesn't mean it doesn't exist.
One day, we will all know, every single one of us. Putting our heads in the sand will not make it not so.