Stephen Hawking was famously an atheist who argued that God is not necessary to our understanding of the universe. 'Because there is a law such as gravity,' he reasoned, 'the universe can and will create itself from nothing'.

But this kind of statement begs the question: if you assume the existence of the laws of physics then you are already assuming the existence of the universe. So it isn't creating itself from nothing – it already exists and is just following through.

What's more, the laws of physics don't just need to exist, they need to be precisely correctly specified if the universe is to be the kind of place in which life can exist.

Noted Cambridge physicist John Polkinghorne explains, in an illuminating passage worth quoting in full:

'Four fundamental forces of nature operate in our universe. Their intrinsic strengths are determined by the values of four corresponding constants of nature. The fine structure constant specifies the strength of electromagnetism; Newton's gravitational constant (G) specifies the strength of gravity; and two constants specify the strengths of the nuclear forces, g(s) for the strong forces that hold nuclei together, and g(w) for the weak forces that cause some nuclear decays and also control the interactions of neutrinos. The magnitudes of all these constants are tightly constrained if the universe is to be capable of producing life. If g(w) were a little smaller, the early universe would have converted all its hydrogen into helium before it had cooled below the temperature at which cosmic nuclear processes ceased. Not only would this have meant no water, so essential to life, but there would also only have been helium-burning stars, which would not have lived long enough to support the development of life on one of their planets. If g(w)had been somewhat bigger, supernova explosions would have been inhibited.'

Even atheist physicists, he notes, have not been able to avoid the implication. Fred Hoyle, who was 'a pioneer in this work', when he realised how precise the strength of the strong nuclear forces had to be to permit the production of carbon inside stars, is reported to have said – despite being an atheist – that the universe was a 'put-up job'. 'He could not suppose that such significant fine-tuning was merely a happy accident.'

And this is only the tip of the fine-tuning iceberg. The mounting evidence is that biological evolution is tightly constrained in the courses it can take, with complex structures like the eye evolving multiple times independently of one another. The structures of life appear to be hard-wired into nature, pre-determined to arise through being energetically favourable and not merely relying on the vagaries of adaptive fitness. Nature is indeed a 'put-up job' – in every way.

The only other explanation to fine-tuning is that our universe is only one of a near infinity of universes in a vast multiverse, one which happens to be conducive to life. This multiverse hypothesis, however, suffers from a dearth of real evidence, which has led John Polkinghorne to describe it as 'a metaphysical guess of excessive ontological prodigality'. It is a multiverse of the gaps, then, and little more than an anti-scientific way of avoiding the logical necessity of God. It is true that in the final years of his life Stephen Hawking tried to prove otherwise, and his final paper has recently been reported as showing how we might detect the traces left by the multiverse in our own universe. This is tantalising – but the scientific community has not been slow to point out its flaws, nor indeed that the reports of its promise appear to have been subject to some 'cosmic inflation'.

But are arguments from science and nature for God's existence actually sound? It is said that to look for a role for God in our understanding of the universe is to advocate a 'God of the gaps', to plug holes in our current understandings with unscientific supernatural explanations. And it is true that if you are arguing that God must personally intervene to explain this or that natural process then you are advancing an ad hoc, anti-scientific theory of natural phenomena. But that is not what we are talking about here. We're talking about whether there is any logically necessary role for God in our understanding of the universe at all.

Philosophers since at least Plato and Aristotle have argued that there is, and that God's existence is strictly necessary and knowable by natural reason. In this the Bible agrees. In the book of Romans it says: 'What can be known about God is plain to them, because God has shown it to them. Ever since the creation of the world his eternal power and divine nature, invisible though they are, have been understood and seen through the things he has made. So they are without excuse' (Romans 1:19-20).

We have already seen one way that we can know that God exists: because the fine-tuning of the universe for the existence of life shows that it must have been designed for that purpose. The odds of it having ended up that way by chance are so vanishingly small that they cannot warrant rational assent.

A second reason we can know God must exist is because, logically speaking, the universe is not and cannot be purely material. Consider how the laws of logic and number are not material, the laws of gravity, of thermodynamics, and of motion aren't material, and neither are the specifications of particles like the electron or of fields like the electromagnetic field. They are immaterial realities which specify the properties and behaviour of the material world. They are what Plato, Aristotle and other philosophers call forms – immaterial, universal specifications of reality which stand behind the material world and determine its structure and nature.

Plato, and the Christian tradition following him, noted that these universal forms resemble ideas in being immaterial and general in nature. They formulated them as divine ideas – the ideas that God has which specify the natural order – and observed that human reason can grasp them precisely because they are ideas, and human beings share in the divine rational nature. This rational principle of the cosmos, which stands behind human reason and enables us to comprehend the inner working of the universe, was termed the logos by Stoic thinkers – an idea which was taken up by the Gospel of John and identified with Christ. It is because the universe consists not just of matter but of this transcendent, rational, immaterial dimension that the human mind can, in its own thoughts, comprehend even a few of the ideas that occupy the Mind of the universe – a Mind which even Stephen Hawking once famously gave a nod to. Or do we really believe that while human beings can understand the laws of mathematics and physics, the universe itself is oblivious to them and just ticks along to them – even though it produced we who can understand them? Neat trick for a dumb machine!

This leads onto our third reason why we know God must exist: because of the existence of consciousness, rationality, free will and morality, all of which require the universe to be more than matter. Morality in particular requires the universe to include ideals – moral ideals like the good human being and the good society – which rational agents may grasp in their understanding and aim at in their conduct. Matter cannot give you morals.

It is for reasons such as these that the existence of God has historically been considered philosophically certain. And not only by Christian philosophers like Anselm and Aquinas, but also by pagan philosophers like Plato and Aristotle and deist thinkers like Voltaire and Thomas Paine, all of whom argued for the necessity of God's existence. It is a truth of natural reason, impeccably logical, and no less rational than the most well-attested claims of science.

In modern times it has become common, even among Christians, to regard the existence of God as a matter of faith which cannot be rationally proved. But that was not the historic position, and it is not what the Bible says. Christian faith may indeed require a step of faith, to accept the claims of Christ about himself – though those too admit of historical investigation. But certainly not simply to believe in God – that is a point of natural theology knowable by natural reason. It has long been held in that account by Western philosophy, pre-Christian, Christian and post-Christian, and despite anything Stephen Hawking said, we still have no reason to doubt it.

Dr Will Jones is a Birmingham-based writer, a mathematics graduate with a PhD in political philosophy and a diploma in biblical and theological studies. He blogs at www.faith-and-politics.com and is author of Evangelical Social Theology: Past and Present (Grove, 2017). He can be found on Twitter @faithnpolitic