Marxists don’t believe in God. No surprises there. But Marxists weren’t the first atheists. In the eighteenth century a series of philosophers and natural scientists demolished the claims of the Church that the existence of God could be proved by reason.

The first theologian to try and use logic to demonstrate God’s existence was St Anselm. This was his argument: if there is a supreme being then no other being, better or greater can be imagined. If the supreme being does not exist, then one could imagine a greater being. Therefore God must exist.

The complete circularity (and barmyness) of such reasoning is obvious. It is an attempt to prove that God’s existence is a logical necessity, like the laws of mathematics. But the axioms of geometry and mathematics can be tested against the material world. Whilst God’s existence is obviously a necessary axiom of religious thought and practice, it does not perform this function in any other sphere of human activity.

Under the pressure of the scientific reasoning which centred on discovering cause and effect, theologians moved the goalposts. They argued that since everything has a cause the universe too must have one, one which exists before the universe. But this argument too breaks down with the unproven assertion that there must be an “uncaused cause” and that this cause must be none other than a single, all powerful and perfect being.

To simply assert that, wherever human scientific knowledge of the chain of causality stops, that is where God starts, proves nothing. Especially since this boundary has been driven backwards time and time again by science.

Another “logical” proof of God’s existence goes as follows: nature is orderly; therefore somebody must have designed it. If you find a watch then there must be a watchmaker.

This argument too has withered under the impact of the advance of the natural sciences, which in sphere after sphere, have shown the internal ordering (and disordering) of organic and inorganic matter. Nowhere can an external, inexplicable “designer” be demonstrated.

Today the most common “proof” is the moral one; that humanity’s notions of right and wrong must all have been implanted by a supreme being, measured against which even the best of human beings must feel imperfect, wicked and sinful. This argument insists that the moral law must be based on absolute values, not on the self-interest of individuals, groups of human beings (nations, classes) or even of humanity as a whole.

This is full of contradictions. Is God “good” by some external absolute standard or is whatever God wills good? In the former case God is not omnipotent because the moral law is a higher force, and the question remains, who designed that?

In the latter case, God is an absolute tyrant making whatever God wills good. What then is the source of evil? Does God will it too or is there some source of it too powerful for God to overcome?

The glib explanation that God allows evil in order to create free will opens the question: did God “allow” the holocaust for this purpose? Could God find no better way? Can God be all powerful and allow evil? The religious person faced with this question, usually resorts to the old get-out clause: “God moves in mysterious ways.”

One final argument is the historical universality of religious experience. But these experiences are infinitely varied and cultually different. And they rest on subjective testimony.

To argue that because people have “experiences”, emotional trauma or exaltation, seeing visions, hearing voices, proves nothing about the objective origin of these experiences, especially since we know that mental disorder, drugs, and emotional or physical stress can and do produce these states.

Today people have visions of Elvis Presley in the same way that, in earlier decades, they had visions of the Virgin Mary. That proves the existence of a need for Gods to worship, a need for the supernatural, but not their existence.

Marxists have little to add to the rational atheists on these so-called proofs. But Marxists have long understood that it is not sufficient to simply disprove the rational force of the claims of religion. It is necessary to explain the varied and changing phenomenon of religion and how it can disappear.

As students, Marx and Engels absorbed the idea from the German philosopher Feuerbach that religious consciousness was a form of alienation.

We turn features of our own nature and experience into supposedly external, all-powerful forces, and then worship them.

Power, goodness and love, were made absolute, unlimited qualities attributed to God, who is then set up as the cause of all that is good in humanity.

The fact that some people today ascribe these features to David Beckham only goes to show that alienation, not God’s existence, is the universal feature of class societies.

Marx and Engels took Feuerbach’s insights into alienation further. They saw that the inverted world of religion was a result of a world in which the great majority of humanity were not in control of their own lives. Humanists like Feuerbach wanted to change humanity without first changing society, without uprooting the oppression and exploitation which are the roots of religious alienation.

Humanity as a species may have largely demystified nature, through science and industry. But it has not demystified human society itself.

Its own social relations of production and reproduction (the family) are the source of endless mystification. Indeed, as long as a tiny minority of the owners of society’s productive forces continue to exploit the majority, the latter will continue to feel powerless, at the mercy of economic laws that act like a blind and often malign fate.

They will seek in the fantasy world of religion the salvation they were denied on earth. Religion, according to Marx, is a psychological consolation for all this suffering, a pain killer or, in the famous phrase, “the opium of the people.”

Marx and Engels did not expect that religion would wither away as long as class society existed. It could not be got rid of by argument, even by mass anti-religious propaganda, let alone by banning it as the Stalinists later tried to do.

Only the overthrow of the profit system could create the conditions for the withering away of humanity’s psychological need for religious belief.