Samuel Clemens, more commonly known by his pen name Mark Twain, was indeed a freethinker of his time. I'm not quite sure if he was an atheist or not: wikipedia notes that he was a Freemason, but he was most certainly not a fan of organized religion----especially Christianity. "The fleets of the world could swim in spacious comfort in the innocent blood it has spilled."
Few literary works have made me laugh out loud as much as Twain's "Letters From the Earth", which is a book consisting of 11 letters written by archangel Satan to archangels Michael and Gabriel. In the letters, Satan discusses man, man's religion, Christianity, and bits of the bible. You can't deny any of Twain's logic, nor would you want to----it's so undeniable that it's insanely humorous. (Note: please remember the times in which Twain wrote. Twain was a liberal of his times, a proponent of civil rights for people of all races and women alike.)
My favorite excerpts:
From the Second Letter
1. First of all, I recall to your attention the extraordinary fact with which I began. To wit, that the human being, like the immortals, naturally places sexual intercourse far and away above all other joys -- yet he has left it out of his heaven! The very thought of it excites him; opportunity sets him wild; in this state he will risk life, reputation, everything -- even his queer heaven itself -- to make good that opportunity and ride it to the overwhelming climax. From youth to middle age all men and all women prize copulation above all other pleasures combined, yet it is actually as I have said: it is not in their heaven; prayer takes its place.
They prize it thus highly; yet, like all their so-called "boons," it is a poor thing. At its very best and longest the act is brief beyond imagination -- the imagination of an immortal, I mean. In the matter of repetition the man is limited -- oh, quite beyond immortal conception. We who continue the act and its supremest ecstasies unbroken and without withdrawal for centuries, will never be able to understand or adequately pity the awful poverty of these people in that rich gift which, possessed as we possess it, makes all other possessions trivial and not worth the trouble of invoicing.
2. In man's heaven everybody sings! The man who did not sing on earth sings there; the man who could not sing on earth is able to do it there. The universal singing is not casual, not occasional, not relieved by intervals of quiet; it goes on, all day long, and every day, during a stretch of twelve hours. And everybody stays; whereas in the earth the place would be empty in two hours. The singing is of hymns alone. Nay, it is of one hymn alone. The words are always the same, in number they are only about a dozen, there is no rhyme, there is no poetry: "Hosannah, hosannah, hosannah, Lord God of Sabaoth, 'rah! 'rah! 'rah! siss! -- boom! ... a-a-ah!"
3. Meantime, every person is playing on a harp -- those millions and millions! -- whereas not more than twenty in the thousand of them could play an instrument in the earth, or ever wanted to.
Consider the deafening hurricane of sound -- millions and millions of voices screaming at once and millions and millions of harps gritting their teeth at the same time! I ask you: is it hideous, is it odious, is it horrible?
Consider further: it is a praise service; a service of compliment, of flattery, of adulation! Do you ask who it is that is willing to endure this strange compliment, this insane compliment; and who not only endures it, but likes it, enjoys it, requires it, commands it? Hold your breath!
It is God! This race's god, I mean. He sits on his throne, attended by his four and twenty elders and some other dignitaries pertaining to his court, and looks out over his miles and miles of tempestuous worshipers, and smiles, and purrs, and nods his satisfaction northward, eastward, southward; as quaint and nave a spectacle as has yet been imagined in this universe, I take it.
It is easy to see that the inventor of the heavens did not originate the idea, but copied it from the show-ceremonies of some sorry little sovereign State up in the back settlements of the Orient somewhere.
All sane white people hate noise; yet they have tranquilly accepted this kind of heaven -- without thinking, without reflection, without examination -- and they actually want to go to it! Profoundly devout old gray-headed men put in a large part of their time dreaming of the happy day when they will lay down the cares of this life and enter into the joys of that place. Yet you can see how unreal it is to them, and how little it takes a grip upon them as being fact, for they make no practical preparation for the great change: you never see one of them with a harp, you never hear one of them sing.
As you have seen, that singular show is a service of praise: praise by hymn, praise by prostration. It takes the place of "church." Now then, in the earth these people cannot stand much church -- an hour and a quarter is the limit, and they draw the line at once a week. That is to say, Sunday. One day in seven; and even then they do not look forward to it with longing. And so -- consider what their heaven provides for them: "church" that lasts forever, and a Sabbath that has no end! They quickly weary of this brief hebdomadal Sabbath here, yet they long for that eternal one; they dream of it, they talk about it, they think they think they are going to enjoy it -- with all their simple hearts they think they think they are going to be happy in it!
It is because they do not think at all; they only think they think. Whereas they can't think; not two human beings in ten thousand have anything to think with. And as to imagination -- oh, well, look at their heaven! They accept it, they approve it, they admire it. That gives you their intellectual measure.
4. The inventor of their heaven empties into it all the nations of the earth, in one common jumble. All are on an equality absolute, no one of them ranking another; they have to be "brothers"; they have to mix together, pray together, harp together, Hosannah together -- whites, niggers, Jews, everybody -- there's no distinction. Here in the earth all nations hate each other, and every one of them hates the Jew. Yet every pious person adores that heaven and wants to get into it. He really does. And when he is in a holy rapture he thinks he thinks that if he were only there he would take all the populace to his heart, and hug, and hug, and hug!
He is a marvel -- man is! I would I knew who invented him.
5. Every man in the earth possesses some share of intellect, large or small; and be it large or be it small he takes pride in it. Also his heart swells at mention of the names of the majestic intellectual chiefs of his race, and he loves the tale of their splendid achievements. For he is of their blood, and in honoring themselves they have honored him. Lo, what the mind of man can do! he cries, and calls the roll of the illustrious of all ages; and points to the imperishable literatures they have given to the world, and the mechanical wonders they have invented, and the glories wherewith they have clothed science and the arts; and to them he uncovers as to kings, and gives to them the profoundest homage, and the sincerest, his exultant heart can furnish -- thus exalting intellect above all things else in the world, and enthroning it there under the arching skies in a supremacy unapproachable. And then he contrived a heaven that hasn't a rag of intellectuality in it anywhere!
Is it odd, is it curious, is it puzzling? It is exactly as I have said, incredible as it may sound. This sincere adorer of intellect and prodigal rewarder of its mighty services here in the earth has invented a religion and a heaven which pay no compliments to intellect, offer it no distinctions, fling it no largess: in fact, never even mention it.
By this time you will have noticed that the human being's heaven has been thought out and constructed upon an absolute definite plan; and that this plan is, that it shall contain, in labored detail, each and every imaginable thing that is repulsive to a man, and not a single thing he likes!
Very well, the further we proceed the more will this curious fact be apparent.
Make a note of it: in man's heaven there are no exercises for the intellect, nothing for it to live upon. It would rot there in a year -- rot and stink. Rot and stink -- and at that stage become holy. A blessed thing: for only the holy can stand the joys of that bedlam.
From the Sixth Letter
The human being is a machine. An automatic machine. It is composed of thousands of complex and delicate mechanisms, which perform their functions harmoniously and perfectly, in accordance with laws devised for their governance, and over which the man himself has no authority, no mastership, no control. For each one of these thousands of mechanisms the Creator has planned an enemy, whose office is to harass it, pester it, persecute it, damage it, afflict it with pains, and miseries, and ultimate destruction. Not one has been overlooked.
From cradle to grave these enemies are always at work; they know no rest, night or day. They are an army: an organized army; a besieging army; an assaulting army; an army that is alert, watchful, eager, merciless; an army that never relents, never grants a truce.
It moves by squad, by company, by battalion, by regiment, by brigade, by division, by army corps; upon occasion it masses its parts and moves upon mankind with its whole strength. It is the Creator's Grand Army, and he is the Commander-in-Chief. Along its battlefront its grisly banners wave their legends in the face of the sun: Disaster, Disease, and the rest.
Disease! That is the main force, the diligent force, the devastating force! It attacks the infant the moment it is born; it furnishes it one malady after another: croup, measles, mumps, bowel troubles, teething pains, scarlet fever, and other childhood specialties. It chases the child into youth and furnishes it some specialties for that time of life. It chases the youth into maturity, maturity into age, age into the grave.
With these facts before you will you now try to guess man's chiefest pet name for this ferocious Commander-in-Chief? I will save you the trouble -- but you must not laugh. It is Our Father in Heaven!
From the Tenth Letter
The first time the Deity came down to earth, he brought life and death; when he came the second time, he brought hell.
Life was not a valuable gift, but death was. Life was a fever-dream made up of joys embittered by sorrows, pleasure poisoned by pain, a dream that was a nightmare-confusion of spasmodic and fleeting delights, ecstasies, exultations, happinesses, interspersed with long-drawn miseries, griefs, perils, horrors, disappointments, defeats, humiliations, and despairs -- the heaviest curse devisable by divine ingenuity; but death was sweet, death was gentle, death was kind; death healed the bruised spirit and the broken heart, and gave them rest and forgetfulness; death was man's best friend; when man could endure life no longer, death came and set him free.
In time, the Deity perceived that death was a mistake; a mistake, in that it was insufficient; insufficient, for the reason that while it was an admirable agent for the inflicting of misery upon the survivor, it allowed the dead person himself to escape from all further persecution in the blessed refuge of the grave. This was not satisfactory. A way must be conceived to pursue the dead beyond the tomb.
The Deity pondered this matter during four thousand years unsuccessfully, but as soon as he came down to earth and became a Christian his mind cleared and he knew what to do. He invented hell, and proclaimed it.
Now here is a curious thing. It is believed by everybody that while he was in heaven he was stern, hard, resentful, jealous, and cruel; but that when he came down to earth and assumed the name Jesus Christ, he became the opposite of what he was before: that is to say, he became sweet, and gentle, merciful, forgiving, and all harshness disappeared from his nature and a deep and yearning love for his poor human children took its place. Whereas it was as Jesus Christ that he devised hell and proclaimed it!
Which is to say, that as the meek and gentle Savior he was a thousand billion times crueler than ever he was in the Old Testament -- oh, incomparably more atrocious than ever he was when he was at the very worst in those old days!
It was extremely difficult to pick out my favorite excerpts, as the entire book is written in just this fashion. I hope any readers enjoyed these excerpts. Mark Twain has several other works such as these, one of my favorites being "The Lowest Animal".