First published in 1896, "A Problem in Modern Ethics" by John Addington Symonds is an historically significant essay and one of the first attempts in modern times to examine homosexuality, putting it in a medical, historical and legal context, and to propose that civil rights should be extended to gay people.
Along with Edward Carpenter and Walt Whitman, Symonds was one of the pioneers of gay rights and spirituality. Symonds was an aristocratic English man of letters who, by virtue of his class status, was able to lead a closeted but very active sexual life. He overcame the fear and loathing that Victorian society attached to homosexuality through an internal struggle which is today known as 'coming out'. However, he had to live a double life, taking lovers from lower social classes while embedded in a sham marriage, and normally had write about his experiences in veiled language.
Even this privately printed essay, which discusses homosexuality frankly, is extremely circumspect. We have to wade through quite a bit of Victorian pseudo-science and gobbledygook to get to the very valid points that Symonds was trying to make. Symonds concludes that homosexuality is innate and not a disease or mental disorder, gay sexuality is every bit as natural as heterosexuality, and homosexual acts between consenting adults should not be treated as criminal. These concepts are quite moderate (although at the time they were, of course, radical), and today are widely accepted.
Symonds later wrote a companion essay to this, "A Problem in Greek Ethics", which drew on his extensive classical knowledge to examine homosexuality in ancient Greece.