Whitman was a vocal proponent of temperance and in his youth rarely drank alcohol. He once stated he did not taste "strong liquor" until he was thirty and occasionally argued for prohibition. One of his earliest long fiction works, the novel Franklin Evans; or, The Inebriate, first published November 23, 1842, is a temperance novel. Whitman wrote the novel at the height of popularity of the Washingtonian movement though the movement itself was plagued with contradictions, as was Franklin Evans. Years later Whitman claimed he was embarrassed by the book and called it a "damned rot". He dismissed it by saying he wrote the novel in three days solely for money while he was under the influence of alcohol himself. Even so, he wrote other pieces recommending temperance, including The Madman and a short story "Reuben's Last Wish". Later in life he was more liberal with alcohol, enjoying local wines and champagne.
Whitman was deeply influenced by deism. He denied any one faith was more important than another, and embraced all religions equally. In "Song of Myself", he gave an inventory of major religions and indicated he respected and accepted all of them—a sentiment he further emphasized in his poem "With Antecedents", affirming: "I adopt each theory, myth, god, and demi-god, / I see that the old accounts, bibles, genealogies, are true, without exception". In 1874, he was invited to write a poem about the Spiritualism movement, to which he responded, "It seems to me nearly altogether a poor, cheap, crude humbug." Whitman was a religious skeptic: though he accepted all churches, he believed in none. God, to Whitman, was both immanent and transcendent and the human soul was immortal and in a state of progressive development. American Philosophy: An Encyclopedia classes him as one of several figures who "took a more pantheist or pandeist approach by rejecting views of God as separate from the world."
Whitman's sexual orientation is generally assumed to be homosexual or bisexual, on the basis of his poetry, though this assumption has been disputed. His poetry depicts love and sexuality in a more earthy, individualistic way common in American culture before the medicalization of sexuality in the late 19th century. Though Leaves of Grass was often labeled pornographic or obscene, only one critic remarked on its author's presumed sexual activity: in a November 1855 review, Rufus Wilmot Griswold suggested Whitman was guilty of "that horrible sin not to be mentioned among Christians". Whitman had intense friendships with many men and boys throughout his life. Some biographers have suggested that he may not have actually engaged in sexual relationships with males, while others cite letters, journal entries, and other sources that they claim as proof of the sexual nature of some of his relationships. Whitman himself, in a response to a letter from English poet and critic John Addington Symonds asking, "In your conception of Comradeship, do you contemplate the possible intrusion of those semi-sexual emotions and actions which no doubt do occur between men?" replied vigorously denying that his work had any such implication, asserting "[T]hat the calamus part has even allow’d the possibility of such construction as mention’d is terrible—I am fain to hope the pages themselves are not to be even mention’d for such gratuitous and quite at this time entirely undream’d & unreck’d possibility of morbid inferences—wh’ are disavow’d by me and seem damnable," and insisting that he had fathered six illegitimate children. Some contemporary scholars are skeptical of the veracity of Whitman's denial or the existence of the children he claimed.
Allen Ginsberg received from Gavin Arthur a document, several times reprinted, in which Arthur described his meeting with early gay activist Edward Carpenter, who told Arthur of his lovemaking with Whitman.
Peter Doyle may be the most likely candidate for the love of Whitman's life.  Doyle was a bus conductor whom Whitman met around 1866, and the two were inseparable for several years. Interviewed in 1895, Doyle said: "We were familiar at once—I put my hand on his knee—we understood. He did not get out at the end of the trip—in fact went all the way back with me." In his notebooks, Whitman disguised Doyle's initials using the code "16.4" (P.D. being the 16th and 4th letters of the alphabet). A more direct, secondhand account comes from Oscar Wilde: Wilde met Whitman in America in 1882 and wrote to the homosexual-rights activist George Cecil Ives that there was "no doubt" about the great American poet's sexual orientation—"I have the kiss of Walt Whitman still on my lips", he boasted. The only explicit description of Whitman's sexual activities is secondhand. In 1924, Edward Carpenter, then an old man, described to Gavin Arthur an erotic encounter that Carpenter had had in his youth with Whitman; Arthur recorded it in detail in his journal. Late in his life, when Whitman was asked outright whether his "Calamus" poems were homosexual, he chose not to respond.
Another possible lover was Bill Duckett. As a teenager, he lived on the same street in Camden and moved in with Whitman, living with him a number of years and serving him in various roles. Duckett was fifteen when Whitman bought his house at 328 Mickle Street. From at least 1880, Duckett and his grandmother, Lydia Watson, were boarders, subletting space from another family at 334 Mickle Street. Because of this proximity, it is obvious that Duckett and Whitman met as neighbors. Their relationship was close, with the youth sharing Whitman's money when he had it. Whitman described their friendship as "thick". Though some biographers describe him as a boarder, others identify him as a lover. Their photograph [pictured] is described as "modeled on the conventions of a marriage portrait", part of a series of portraits of the poet with his young male friends, and encrypting male–male desire. Yet another intense relationship of Whitman with a young man was the one with Harry Stafford, with whose family Whitman stayed when at Timber Creek, and whom he first met when Stafford was 18, in 1876. Whitman gave Stafford a ring, which was returned and re-given over the course of a stormy relationship lasting several years. Of that ring, Stafford wrote to Whitman, "You know when you put it on there was but one thing to part it from me, and that was death."
There is also some evidence that Whitman may have had sexual relationships with women. He had a romantic friendship with a New York actress, Ellen Grey, in the spring of 1862, but it is not known if it was also sexual. He still had a photograph of her decades later, when he moved to Camden, and he called her "an old sweetheart of mine". In a letter, dated August 21, 1890, he claimed, "I have had six children—two are dead". This claim has never been corroborated. Toward the end of his life, he often told stories of previous girlfriends and sweethearts and denied an allegation from the New York Herald that he had "never had a love affair". As Whitman biographer Jerome Loving wrote, "the discussion of Whitman's sexual orientation will probably continue in spite of whatever evidence emerges."
Whitman was an adherent of the Shakespeare authorship question, refusing to believe in the historic attribution of the works to William Shakespeare of Stratford-upon-Avon. Whitman comments in his November Boughs (1888) regarding Shakespeare's historical plays:
Conceiv'd out of the fullest heat and pulse of European feudalism—personifying in unparalleled ways the medieval aristocracy, its towering spirit of ruthless and gigantic caste, with its own peculiar air and arrogance (no mere imitation)—only one of the "wolfish earls" so plenteous in the plays themselves, or some born descendant and knower, might seem to be the true author of those amazing works—works in some respects greater than anything else in recorded literature.
Whitman opposed the extension of slavery in the United States and supported the Wilmot Proviso. At first he was opposed to abolitionism, believing the movement did more harm than good. In 1846, he wrote that the abolitionists had, in fact, slowed the advancement of their cause by their "ultraism and officiousness". His main concern was that their methods disrupted the democratic process, as did the refusal of the Southern states to put the interests of the nation as a whole above their own. In 1856, in his unpublished The Eighteenth Presidency, addressing the men of the South, he wrote "you are either to abolish slavery or it will abolish you". Whitman also subscribed to the widespread opinion that even free African-Americans should not vote and was concerned at the increasing number of African-Americans in the legislature.