The current Justifying Ideology of Capitalism is what I mainly mean by Capitalism for the purpose of this post.
Adam Smith is often called the "Philosopher of Capitalism" as if he is to Capitalism what Karl Marx and Fredrich Engels are to Communism. Adam Smith was also an Atheist, there is some dispute about this technically, some try to argue he was more a Deist (which was basically Atheism with plausible deniability) but from my research he was definitely an Atheist.
Before Smith wrote The Wealth of Nations he wrote The Theory of Moral Sentiments which was basically an attempt to explain the development of morality naturalistically. His Economic Philosophy was built on this secular moral philosophy. David Hume was an English Economic Philosopher who came just a little before Smith and overlapped with him, in some ways his ideas are more inline with the beliefs of modern apologists of Capitalism them Smith's and he was even more of an Atheist.
A French laissez-faire Economist contemporary with Hume and Smith was Paul d'Holbach who was also an Atheist, as was Denis Diderot and Jacques-Andre Naigeon, meanwhile Voltaire and Montesquieu were Deists and also didn't speak much on Economics directly. The Physiocrats were also definitely Secularists though exactly what they believed about Religion I can't pin down. And don't think you can pretend Voltaire could have bene a socialist, he was a Bourgeoise intellectual who "never intended to enlighten shoemakers and servants". The only Socialist among the major French Philosophs was Rousseau who was also the most Christian of them.
The most actually religious Economist of the late 18th early 19th Century was Thomas Malthus, but while some of Malthus's most well known ideas were influential on future Capitalist Economists he himself was not one, he was critiquing the rise of Capitalism from a more old fashioned late Feudalist perspective.
Later in the 20th Century a woman named Ayn Rand would develop a philosophy that is essentially Capitalism in it's purest most unrestrained and unapologetic form. She was also a rabid Atheist who was frequently enraged at seeing American Christians try to co-opt her ideas to serve their Christianized Capitalism. Rand was also a stated influence on the philosophy of Anton Levy the founder of the Church of Satan, which is exactly the Satanism people mean when they say Satanists are actually Atheists and Satan is just a symbol to them, their Satan is a symbol of Capitalist Individualism. Another influence on Levy was the 1896 individualist text Might Is Right.
Between Smith and Rand it continued to be Atheists making vital contributions to Individualist philosophy, from the Atheist Existentialist Philosophers cited in Josh McNamee's Man of Steel video, to Charles Bradlaugh to Nietzsche and Social Darwinists like Herbert Spencer, to H.L. Mencken, Charles Lee Smith, James Hervey Johnson and Irving Fisher. John Stuart Mill was also an Atheist though this wasn't publicly known while he was alive, between Mill and Smith were Jeremy Bentham, Francis Place and James Mill. And to more specifically look at mid 20th century Economists, whether you're looking at the Austrian School, the Keynesian School or the Chicago School, secularists like Milton Friedman, Keynes, Murry Rothbard and Hayek are always at the center.
Capitalism as a Mode of Production was very much forming already before we reach Hume, d'Holbach and Smith, but that happened because of economic developments that were not exactly pre-planned or premediated. The Philosophers of Liberalism who came before them were not thinking much about economics but mostly focusing on what they and the Socialists had in common, opposing Absolute Monarchy. The 1640-1660 English Revolution was Socio-Economically speaking an internal dispute within Feudalism as it had been operating in England for Centuries, the only group involved in all of that who were calling for a total reworking of how society is Economically structured were the Diggers lead by Gerrard Winstanley who were Anarcho-Communists, and they were basing their ideas on The Bible.
John Locke is the one commonly cited exception to all that, he is frequently given the credit for truly innovating the modern Capitalist notion of Private Property. But James Tully in A Discourse on Property: John Locke and his Adversaries showed that what Locke actually said is more compatible with Socialism. David Hume was actually quite critical of Locke, the problem is Locke's Labor Theory of Value would be co-opted by d'Hollbach, Smith and their followers. The Labor Theory of value is often associated with Capitalism because of it's association with Locke and Smith, but the truth is only Socialists and Communists believe in it unconditionally, Capitalists keep needing to qualify it.
Nicolas Barbon was another Christian Whig who contributed to economics, but he was mainly advocating for Paper Money which in the short term Communists are more supportive of then Austrian School Liberals. John Law continued his work in that regard. Their ideas were first put into practice in a Proto-Capitalist context but still not necessarily inherently Capitalist.
Some people both for and against it like to tie the origins of Capitalism to the "Protestant Work Ethic", and yeah to a certain extent early Primitive or Proto Capitalism emerged in Protectant parts of Europe earlier then it did in Catholic countries. You could even parallel different forms or elements of Capitalism to different forms of Protestantism, Lutheranism was it still mixed with late Feudalism, Arminianism the hyper Individualism, Calvinism would be Fascist-Capitalism, and then Britannia is where they all mixed together before being transported to her Colonies.
But it's important to remember that during the first 2 or 3 centuries the Reformers really wanted to be seen as more rationalist then the Catholics and rejecting of their superstitions, that's why Cessationism was invented by the Reformers and why for a long time they didn't do Exorcisms.
And that in turn is why a lot of things Atheists believe in are partly protestant in origin but simply taking the next step. A lot of the bad history New Atheists perpetuate began as protestant myths to demonize the Catholic Church, the Hypatia and Library of Alexandria stuff came form Edward Gibbon (as does many bad ideas about how and why Rome fell) and the comparative mythology stuff started with Alexander Hislop, and the Christmas is actually Pagan stuff started with the Puritans. As I've said on this blog before, Existentialism is basically Atheistic Arminianism, and others have called Objectivism Prosperity Gospel for Atheists.
All that said I also have a lot of skepticism of the "Protestant Work Ethic" thesis.
A lot of Internet discourse over the last decade or so has been tied to how the Skeptic Community on YouTube and other New Atheists revealed their true reactionary colors (Christopher Hitchens' Legacy is lucky he passed away just before all this started, because if you look into him you'll see he'd absolutely have been with them), and that came with them being bold evangelists of Capitalism, seeing Capitalism along with Democracy as a great Enlightenment accomplishment of Secularism overthrowing the "Dark Ages" of Feudalism which they incorrectly blame on religion.
Atheists on the True Left still exist, but people making Atheism the first thing they care about, the core of their identity, are even when trying to distance themselves from the Reactionary New Atheists usually Social Democrats at best.
New Atheism isn't actually new, Antitheists co-opting Gibbon's bad history began with Voltaire. And then during The French Revolutions the immediate successors of d'Holbach were the Hebertists who showed a lot of Proto-Fascistic tendencies with their forced Dechristianization campaign and helping send many of the Communists (called the Enragés at the time) or even just Liberals who wanted to Redistribute Property like the Girondins to the Guillotine.
Even the Antifeminism that started the 2011 downward spiral was already there in how they Martyred early Feminists like Olympe de Gouges, she was beheaded 7 days before the Festival of Reason and she was later used specifically as an example to silence other women by supporters of the Dechristianization campaign.
Then in the 19th Century Bruno Bauer began popularizing the absurd thesis that Jesus did not exist which went hand in hand with his well known opposition to Karl Marx. You see Marx and Engels were Atheists but like sane Atheists they believed Jesus existed and that the Early Christians were ancient Proto-Communists and thus part of his thesis of all history being Class Struggle. So to Bauer refuting the very existence of Jesus was an attack on the Marxist understanding of History as much as it was mainstream Christianity. Bauer was also the Anti-Semite who wrote The Jewish Question.
And speaking of the Marxist understanding of history, every time a New Atheist talks about Wars being caused by Religion, that is fundamentally incompatible with a Marxist analysis of history which always looks for the economic causes and sees them as the primary cause. And in turn Evangelical/Conservative Christians seeking to "debunk" the notion of Religious Wars by emphasizing the Economic Causes are unwittingly engaging in Marxist analysis.
Max Stirner was another Atheist Individualist Philosopher who connected Christianity and Communism in his opposition to both.
Another problem with letting yourself get lost in the nominal Anti-Religionism of Marx and Engels is that Marx actually had a lot of good things to say about Capitalism, he considered it an improvement over Feudalism and a good contributor to Human advancement that was simply now beginning to outlive it's usefulness. Contemporary Christian Socialists like Philpe Buchez, Edward Vansittart Neale and Frederick Denison Maurice were actually more Anti-Capitalist then Marx was though sometimes they did have their own problems, I have come to believe there's a lot Christian Communists can and should learn from Marx and later Marxists, but I still disagree with Marxism on some key issues.
Marx and Engels "Opiate of the masses" quote is misunderstood, at that time no one thought of Opium mainly as a harmful addictive drug but rather it was still most well known for it's medicinal use. Neither meaning of "Opiate of the masses" fits how New Atheists view Religion however, they see it as Crack.
Honestly I'm growing skeptical of Marx and Engels even being as Atheist as they seemed. After all Liebknecht family tradition says they were Karl Liebknecht's God Parents at his Baptism at the St. Thomas Lutheran Church.
Christian Capitalists exist because since we became the Mainstream Religion of The West we've made it possible to force anything to be compatible. But when it comes to Socio-Economic Systems it's always been clear Capitalism is the most difficult to make fit given everything The New Testament says, the truest Reactionary Christians inevitably give away that they really want to go back to Feudalism where the ruling class had some incentive to at least pretend they cared about those beneath them, Noblesse oblige.
There are degrees to how much various kinds of Christians in the modern era have embraced Capitalism. Megachurches and the Prosperity Gospel are Capitalist Christianity at it's worst, to me they are the modern Laodicea. But I find it interesting how many Christians on YouTube seeking to preach agaisnt them are unwilling to straight up say or admit that Capitalism is the root of the Problem, like a Secular Centrist they don't want to admit that you can't separate that extravagant Greed from our Socio-Economic Mode of Production, everything about how the world works encourages it, they are people eager to condemn the most egregious symptoms but unwilling to address the root cause of the Disease.
Then maybe you'll have some willing to go a bit further then that. They might say "Christians shouldn't be Capitalists but the world is certainly less evil under Capitalism then it is when it's COMMUNIST". Or maybe they'll say "yes Capitalism is bad but that doesn't mean we should support SOCIALISM". The problem is opposing Capitalism without supporting Socialism leads to Fascism, Nazism or Neo-Feudalism. You need to also promote the good alternative.
And there is also the way that these people preaching agaisnt Laodiceanism will focus on it's Aesthetics just as much if not more then the Substance of what's wrong with them and wind up tying their Social Conservativism into it, including the Sexual Morality that comes from Plato not The Bible.
The branding of Communism as Godless and Capitalism as Godly was the result of Cold War Propaganda. Communism was inherently Christian for 100% of it's history until The French Revolution when some Communists started borrowing from the Atheism of the Liberals they were fighting alongside against the Monarchy and Feudalism. Capitalism is what wouldn't exist without the Secularism of the Enlightenment, and now thanks to the Climate Crisis the entire world is paying the price for the Godlessness we embraced.
The YouTube Channel Praxis & Theodicy has a series on the Sin of Usury and how Capitalism as a system is dependent on Usury.
Update August 2023: I rewatched a bunch of the Anime Tanya The Evil recently and that show is kind of aware of what I'm arguing here, the main character absolutely connects their Atheism to their "Free Market Principals".
You should also check out the sister post to this The Reformation and The Resurgence of Democracy.
