In order to understand the times we live in, it is essential that we know where we have come from. While this is true of personal history it is also true of our collective history – which is perhaps why The Rest is History, fronted by Tom Holland and Dominic Sandbrook, has become one of the most popular podcasts in the English-speaking world. The mixture of deep historical knowledge, contemporary application, British humour and joyful camaraderie make for a wonderful listening experience.

Every now and then they come up with an episode which is revelatory – almost prophetic. A recent example was on that unlikeliest of historical subjects, the infamous Marquis de Sade. In less skilled hands the temptation to turn this into a kind of mocking sleaze fest would have been too much, but not to our two intrepid presenters.

In fact, what transpired was enlightening. When we find ourselves wondering how the Western world has ended up in its present state of confusion and disintegration, the Rest is History's analysis of de Sade helps us to the answers. In summary, Holland and Sandbrook argued that the ideologies and ideas of Freud, Darwin and Nietzsche were there in seed form in de Sade.

De Sade, a Frenchman, was born in 1740. He was a writer, philosopher, politician and playboy. He lived through the French revolution and even became a key participant in it, becoming an elected delegate to the National Convention. He died in September 1814 having lived a life of debauchery, sexual perversion and violent abuse. He recorded his ideology in various writings including the books Justine and The 120 Days of Sodom - works that are so grotesque they were banned in the UK until 1989.

They are horrific – so horrific that Tom Holland records that though he had tried to read The 120 Days of Sodom several times, he gave up. He described it as literally "unreadable", because of its evil and sickening content. It is an interesting observation that websites like Amazon feel quite free to offer this book for sale (and Penguin are now quite happy to publish it as a 'classic') but dare to misgender someone and your books could be banned! At a personal level I would strongly discourage people from reading this dark perversity – I know of people who have been severely harmed by reading it at university.

His promotion of what became known as sadism, as well as masochism and homosexuality was, for its day, so extreme that he ended up in prison for over 30 years of his life. But as Holland and Sandbrook point out, much of his philosophy would today now be regarded as 'progressive'. Here are his principles which sound so modern.

1. All is naturalistic materialism

He was a social Darwinist, believing in the survival of the fittest. He had faith that everything was material. All are molecules and molecules are endlessly turning. Therefore, war and murder are natural and desirable. It is natural for wolves to eat lambs – and we should never oppose nature.

2. Reject Christianity

It is not without significance that de Sade was a committed atheist, who like Nietzsche, rejected not only the religion of Christianity but also its values and virtues. De Sade hated and despised Christ and the Church. He continually blasphemed against all aspects of Christianity and attacked Christ, as well as portraying the clergy as perverted hypocrites. He regarded Christianity as a slave religion which was fit only for the weak.

In this he was a forerunner of Hitler. Traudl Junge, Hitler's personal secretary, described Hitler's de Sade/Nietzsche philosophy in the book, Until the Final Hour:

"Sometimes we also had interesting discussions about the church and the development of the human race. Perhaps it's going too far to call them discussions, because he would begin explaining his ideas when some question or remark from one of us had set them off, and we just listened. He was not a member of any church, and thought the Christian religions were outdated, hypocritical institutions that lured people into them. The laws of nature were his religion. He could reconcile his dogma of violence better with nature than with the Christian doctrine of loving your neighbour and your enemy. 'Science isn't yet clear about the origins of humanity,' he once said. 'We are probably the highest stage of development of some mammal which developed from reptiles and moved on to human beings, perhaps by way of the apes. We are a part of creation and children of nature, and the same laws apply to us as to all living creatures. And in nature the law of the struggle for survival has reigned from the first. Everything incapable of life, everything weak is eliminated. Only mankind and above all the church have made it their aim to keep alive the weak, those unfit to live, and people of an inferior kind."

3. Follow your desires

For de Sade culture is relative. You can trust only yourself and your feelings – especially your sexual desires. They are your authentic self so you must do what you want and live your own truth. Freud accepted Sade's proposition that sexual identity is fundamental to your identity and that it is bad to suppress it. We have now so adopted this as state ideology in the Western world, that to seek to suppress any one's desires is regarded in some states as a hate crime. Whereas de Sade went to jail for sexual perversion, soon we will be sent to jail for calling it perversion!

4. Follow 'Progressive' values

It was fascinating to discover that Michel Foucault and Jacques Derrida, the fathers of postmodernism, were greatly influenced by de Sade and wrote appreciative studies of him. Even feminists like Simone de Beauvoir feted him – despite his sickening treatment of women and young girls.

Like de Sade they too argued that morals were rooted in nature rather than in Christianity. De Sade was against the death penalty (although accepting that murder was natural), believed that women had the right to abortion and was in favour of gay rights. He pushed these principles to the extremes – but if you believe in absolute tolerance then his violence and sadism are difficult to condemn. He argued that rape and incest should be legitimate and that murder, even to the extent of genocide, was sometimes good because it was just nature's way of limiting the human population and saving Mother Earth.

In writing about the joy of rivers in China being clogged up with the bodies of dead children he foreshadowed Chairman Mao's view of the Great Famine (man-made) where up to 30 million died. When told this Mao responded "is that all?". After all it was just a rearranging of molecules; the strong getting rid of the weak for the sake of humanity and the planet and the good of the state!

5. A progressive state should always be looking for frontiers to push back

With every 'progressive' advance (or as I would put it, regression back into the pre-Christian pagan past) we sometimes hope 'that will be the end of that, now they've got what they wanted'. But for progressives, when they get their values, it's like drinking salt water. Their thirst is never satisfied. Like de Sade they want to push the boundaries just another step. And then another. And then another.

None of this is to say that everyone who adheres to 'progressive' doctrines is a Sadist. Most people are too inconsistent and confused to follow everything through to its logical conclusion. However, we need to point out that Sadism is the logical and natural outcome of these doctrines and that it in turn leads to Fascism and Communism. It is ironic that the most 'progressive' states in the West say they are the enemies of Fascism (although they for some reason seem to leave out its twin, Communism), while themselves espousing the Sadist doctrines and adopting a softer, but nonetheless authoritarian ideology.

As Paul tells us in 1 Timothy 4:1 'in later times some will abandon the faith and follow deceiving spirits and things taught by demons'. Does anyone doubt that the primary doctrines that de Sade promoted are anything other than 'demonic'? Christians need to understand this and know that the best way to fight the darkness is to be the light. The best way to preserve the taste of society is to be salt. The best way to defeat anything anti-Christ is to proclaim Christ in word and deed. The rest is history.

David Robertson leads The ASK Project in Sydney, Australia. He blogs at The Wee Flea.