Moroni is probably not suggesting here that it is by the power of the Holy Ghost that people come to know the truths of physics or chemistry or biology, though God frequently endows the honest in heart with insights and discoveries. Rather, he seems to be suggesting that it is by the power of the Holy Ghost that we know the truth, that we know when something is true and when something is not. It is by the power of the Holy Ghost that we can have discernment and divine judgment. Indeed, it is by means of this unction, this anointing from on high, that the people of God come to know things they could never learn from man, pure things which come from a pure source (see 1 John 2:27; JST, Matthew 3:24-26; compare John 14:26; D&C 43:15).