Joseph Smith wrote that he felt that black peoples should be "confined by strict law to their own species," which some have said directly opposes Smith's advocacy for all other civil rights. In Nauvoo, it was against the law for black men to marry whites, and Joseph Smith fined two black men for violating his prohibition of intermarriage between blacks and whites. In 1852, the Utah legislature passed Act in Relation to Service which carried penalties for whites who had sexual relations with blacks. The day after it passed, church president Brigham Young explained that if someone mixes their seed with the seed of Cain, that both they and their children will have the Curse of Cain. He then prophesied that if the Church were approve of intermarriage with blacks, that the Church would go on to destruction and the priesthood would be taken away. The seed of Cain generally referred to those with dark skin who were of African descent. In 1863 during a sermon criticizing the federal government, Young said that the penalty for interracial reproduction between whites and blacks was death. In 1946, J. Reuben Clark called racial intermarriage a "wicked virus" in an address in the church's official "Improvement Era" magazine. The next year, church member Virgil H. Sponberg asked if members of the church should be required to interact with blacks. The First Presidency under George Albert Smith sent a reply on May 5 stating that social interaction with blacks should not be encouraged because it would lead to interracial marriage. Two months later in a July 17, 1947 letter to Lowry Nelson, the First Presidency stated that marriage between a black person and a white person is not sanctioned by the church and is "contrary to church doctrine". Two years later in response to inquiries from a Californian stake president about whether white members were required to associate with black people the apostle Clark wrote that the church discouraged social interaction with black people since it could lead to marriage with them and interracial children. Church apostle Mark E. Petersen said in a 1954 address that he wanted to preserve the purity of the white race and that blacks desired to become white through intermarriage. The speech was circulated among BYU religion faculty, much to embarrassment of fellow LDS scholars. Over twenty years later Petersen denied knowing if the copies of his speech being passed around were authentic or not, apparently out of embarrassment. In 1958, church general authority Bruce R. McConkie published "Mormon Doctrine" in which he stated that "the whole negro race have been cursed with a black skin, the mark of Cain, so they can be identified as a caste apart, a people with whom the other descendants of Adam should not intermarry."