This term means only begotten of mortal flesh. All the spirit children of Heavenly Father were begotten by immortal beings, Heavenly Father and one of His wives. The first parents of all the worlds were also begotten by Heavenly Father and one of His wives, but, as Brigham Young explained, they ate of the fruit of the terrestrial world so instead of having a spirit child, they provided physical tabernacles for the spirits of the first parents of the various worlds. However, Christ was begotten by Heavenly Father and a mortal woman, whom He sealed to Himself, through this same process, as also explained by Brigham Young and James Talmadge (see "Mormon Doctrine" under "Son of God"). Thus, the expression "Only Begotten in the {mortal} Flesh."