Moroni 10:4-5

Joseph Smith found God directly by following the admonition of James 1:5 --

" 5 If any of you lack wisdom, let him ask of God, that giveth to all men liberally, and upbraideth not; and it shall be given him. "

Later he re-canonized the same concept in Moroni 10:4-5 in the Book of Mormon:

4 And when ye shall receive these things, I would exhort you that ye would ask God, the Eternal Father, in the name of Christ, if these things are not true; and if ye shall ask with a sincere heart, with real intent, having faith in Christ, he will manifest the truth of it unto you, by the power of the Holy Ghost.

5 And by the power of the Holy Ghost ye may know the truth of all things.

These concepts were taught to me growing up as objective empirical tests that could prove the truth of the religion. It was supported by other empirical road marks, the most notable being the objective witnesses (3 and 12), who saw respectively angels and gold plates. The concept that an emipirical test can be applied to subjective spiritual truth isn't foreign, but it is also completely predictable that if objective, empirical evidence is found lacking that a "believer" in the Mormon faith, might be deconverted.