Dallin H. Oaks
"In describing the state of the inner man, the scriptures commonly use the word heart. This word occurs over a thousand times in the standard works, almost always as a figurative expression.
"Heart is often used to identify the extent to which one is receptive to the message of the gospel. Nephi said, 'The Lord . . . did visit me, and did soften my heart that I did believe' (1 Nephi 2:16). A later Nephi described his preaching to a people who 'did harden their hearts and did not hearken unto the words of the Lord' (Helaman 10:13)
"Heart is sometimes used as a synonym for mind. Speaking of the multitude who heard the risen Lord on this continent, the Book of Mormon says, 'neither can the hearts of men conceive so great and marvelous things as we both saw and heard Jesus speak' (3 Nephi 17:17). 'Their hearts were open and they did understand in their hearts the words which he prayed' (3 Nephi 19:33).
"Heart is also used in contrast to mind, with mind apparently connoting the powers of reasoning (the intellectual) and heart connoting the powers of intuition (the spiritual). President Harold B. Lee used those two words in this contrasting sense when he said: 'When we understand more than we know with our minds, when we understand with our hearts, then we know that the Spirit of the Lord is working upon us' (Harold B. Lee, Stand Ye in Holy Places [Salt Lake City: Deseret Book Co., 1974], p. 92)." (Pure in Heart, Preface)