The rise of homosexual literature in the 19th and 20th centuries had two major effects. First, it increased the representation of homosexuality in the landscape of American literature by providing complex, realistic and thought-provoking literary models of the unique concerns of individuals with diverse sexual identities and orientations. Second, it expanded the realm of acceptable sexual material for the mainstream, so that heterosexual writers were able to engage issues of sexual identity that had been taboo prior to the rise of 19th century homosexual literature. In 1908, Edward Stevenson published A History of Simisexualism, in which he discussed homosexuality not as a mental or sexual disorder, but as a natural and indeed liberating sexual identity. During this time, several homosexual memoirs were published across Western Europe and in the U.S. These literary expressions paved the way for a more empathetic and respectful view of homosexuality within the literary world and within American political and social life as well.